You can continue to follow the latest from the Barcelona terror attack here.
Terror in Barcelona as van hits crowd in Las Ramblas
Driver arrested after escaping scene on foot
Spanish media reports 13 people killed
A white van plowed into a packed summer crowd this evening in Barcelona's historic Las Ramblas district. Barcelona police called it a terror attack and local media reported 13 dead and dozens more injured.
The driver was arrested around two and a half hours after the attack, reports said.
The vehicle hit pedestrians in Las Ramblas, a busy tree-lined promenade in the centre of the city.
Catalan police tweeted "there are mortal victims and injured from the crash" without specifying any numbers. Spanish media, including Cadena SER radio station and TV3, reported up to 13 dead, while other media had varying death tolls.
"Huge collision on Las Ramblas in Barcelona by an individual driving a van, many injuries," a statement from Catalan police added.
The street is one of the most well-known and popular parts of the city, visited by tourists and locals alike.
Images posted on social media appear to show people being tended to as they lay on the street.
Reports said the driver escaped the scene on foot and was holed up in a bar in Tallers Street. Armed police ran down the streets and through a market, checking in stores and cafes.
In photographs and videos, at least five people could be seen lying on the ground in the streets of the northern Spanish city on Thursday afternoon, being helped by police and others. Other video recorded people screaming as they fled the van.
Carol Augustin, a manager at La Palau Moja, an 18th-century place on Las Ramblas that houses government offices and a tourism information center, said the van passed right in front of the building.
"We saw everything. People started screaming and running into the office. It was such a chaotic situation. There were families with children. The police made us close the doors and wait inside," she said.
While full details of the incident were not immediately clear, since July 2016 vehicles have been used to ram into crowds in a series of militant attacks across Europe, killing well over 100 people in Nice, Berlin, London and Stockholm.
Theresa May: 'UK stands with Spain against terror'
Britain "stands with Spain against terror", Prime Minister Theresa May said following the deadly attack.
"My thoughts are with the victims of today's terrible attack in Barcelona and the emergency services responding to this ongoing incident. The UK stands with Spain against terror," the prime minister wrote on Twitter.
Donald Trump: we'll do whatever is necessary to help
Melania Trump send her thoughts and prayers
The US first lady tweeted:
Spanish public broadcaster RTVE says one suspect in the Barcelona van attack has been arrested.
Passport 'found at scene'
Barcelona's Tv3 reports that the Spanish passport of a person of Moroccan origin was found at the scene of the attack.
Second van 'found by police'
Reuters, citing local authorities, reports that a second van has been found by police in the town of Vic, north of Barcelona.
Jeremy Corbyn tweets his support
London stands with Barcelona
Sadiq Khan, the Mayor of London, has tweeted:
'There was a mini stampede'
Ethan Spibey, a charity director on holiday in the city, said he had taken shelter in a nearby church with several others after Thursday's van ramming.
"All of a sudden it was real kind of chaos... people just started running screaming," he told Sky. "There was kind of a mini stampede.
"It seems like a lot of people have taken refuge in shops and local cafes."
A video circulating on social media showed at least 19 people lying injured on the pavement down the centre of Las Ramblas.
Many victims can be seen bleeding, some heavily, while being tended to by passersby.
Souvenirs are strewn across the path, having apparently been knocked over in the chaos.
Armed police are visible in the background.
One death confirmed by police
A police official in Barcelona has said that one death has been confirmed, and 32 others have been injured in the van attack, ten of which are seriously injured.
At least 56 people have been taken to hospitals across the city, according to local newspaper La Vanguardia.
Van 'was going very fast, without caring about who was in its way'
TV3 says it now has official confirmation that thirteen people are dead. It also says there are dozens of injured.
Eyewitness Lourdes Porcar told TV3 television station that she saw the van running people over. “It was going very fast, without caring about who was in its way,” she said.
Police have set up roadblocks around the city amid reports that a second van was involved in the attack and fled the scene.
There are also reports that at least on attacker is holed up in a Turkish restaurant on Carrer Hospital, which leads off from the spot in which the van appears to have come to a halt.
Television pictures show that a van came to a halt on top of a Joan Miro mosaic, half-way down Las Ramblas - meaning that it would have covered more than 500 metres.
Las Ramblas potentially deadliest attack since 2004 bombing
The deadliest recent attack in Spain was in March 2004, when Islamist militants placed bombs on commuter trains in Madrid, killing 191 people and wounding more than 1,800.
Death toll 'could be as high as 13'
Reuters reports that at least 13 people have been killed in the attack, citing local media.
President has been informed, says White House
The White House's chief of staff said it was keeping President Trump closely informed about the situation.
'Second van' linked to attack
Police are looking for a second van that may have been involved in the attack, Sky News reports
Tourists speak of shock
Police stationed at the cordon a block away from Plaza Catalunya, on Passeig de Gracia, say they have no information what is happening inside. Confused tourists, shoppers and business owners gathered at its edges, awaiting some word or direction as to what to do.
Ines Prauka, a 49 year old tourist from Berlin arrived with her 14 year old daughter Adel for a one week holiday just an hour or two before the attack.
They had just checked in to an apartment at the top of the Ramblas and come out in search of a supermarket to find pandemonium on the street.
"Everybody was running and panicking and crying," she said. Ambulances arrived and police told them to run away, but they did not understand as the orders came in Spanish, she said, and had to ask.
Ms Prauka was clearly in shock and struggled to speak at times. "It's unbelievable. Two hours in Barcelona and this. We are shocked.
"It's the first time we've been in a situation of everyone crying and panicking around us, we didn't know if it was terrorism, a bomb."
Berlin had been touched by terrorism but they had never experienced it personally, she said, adding that she did not know where to take her daughter now.
"A one week summer holiday in Barcelona and that was the start," she said.
Barcelona police to hold press conference
Local police are expected to begin a press conference in around ten minutes. Stay with us for the latest updates.
'There was panic everywhere," says eyewitness
Daksha Dixit, a 28 year old tourist visiting from Mumbai with family, said they had been on a tourist bus which had just dropped them off one block from Plaza Cataluña when they heard the news.
"We got off and people were panicking, no one knew what was going on. There was panic everywhere."
The family arrived just yesterday for a one week trip and their hotel is on the Ramblas inside the cordon.
They were unclear as to what exactly was unfolding, with Miss Dixit adding: "I don't know what to do".
Attacker used rented van
Catalan police say they are treating the crash as a suspected terrorist attack but cannot yet confirm the motive.
It has also been reported that the attack vehicle was a rented van. That would suggest, if this is confirmed as a terrorist attack, that same terrorists are imitating the perpetrators of the London Bridge attack, where a rented van was also used.
'We heard gunshots...there was screaming and shouting'
Steve Garrett was in a nearby market and sheltered in a bakery with several others after streams of people ran inside.
One member of the group, who took refuge with him, said she had heard gunshots after the incident.
Mr Garrett told the BBC: "A very large number of people ran into the market area in a big kind of way, lots of screaming, lots of shouting.
"The security guards immediately responded. We ran into the bakery with four or five other people and ran straight upstairs and hunkered down whilst an enormous wave of people went through the market.
"Obviously coming from England it was reminding me a great deal of what happened in London, so we were very concerned about what might be going on next.
"The lady that was with us said she heard some gunshots."
Mr Garrett said a "second wave" of people then entered the market, followed by armed police.
He said: "They seemed to sweep through the market area. They seemed to be looking for someone. They were going very carefully, very cautiously, stall to stall."
Jordi Lino was on a bus going down the Ramblas when he saw the attack: "First I saw people running and then the van. There were injured people in the middle of the Ramblas."
Footage appears to show crash vehicle
Confusion and panic in Las Ramblas
Telegraph reporter Hannah Strange has arrived at Las Ramblas, where she says there is a very heavy police presence, confusion, and helicopters flying overhead.
Local media is reporting is that several people have died.
The Spanish newspaper El Pais quoted unnamed police sources as saying the perpetrators of the crash were holed up in a bar in Tallers Street. There was no immediate police confirmation of the report.
Inside the glossy stores of Passeig de Gracia, shoppers and staff sheltered behind glass windows. Many streamed away from the cordon but others stayed on the street in an eerie limbo, the ambulances racing past the only clue as to the status of the situation.
Armed police pictured at scene
Restaurant hostage situation is ongoing
Two armed men have entrenched themselves in a Turkish bar and restaurant in Barcelona's city centre after a van mowed down dozens of people, El Periodico newspaper reported on Wednesday.
El Periodico reported gunfire in the area of La Boqueria Market, although it did not cite the source of the information.
It was not immediately clear that the men were the drivers of the van.
Several bodies lay in street in aftermath of attack
In a photograph shown by public broadcaster RTVE, three people were lying on the ground in the street of the northern Spanish city Thursday afternoon, apparently being helped by police and others.
Videos of the scene recorded people screaming as they fled.
Police cordoned off the broad, popular street, ordering stores and nearby Metro and train stations to close. They asked people to stay away from the area so as not to get in the way of emergency services. A helicopter hovered over the scene.
'It was chaos...everyone was in panic mode'
Aamer Anwar was walking down Las Ramblas at the time, which he said was "jam-packed" with tourists.
He told Sky News: "All of a sudden, I just sort of heard a crashing noise and the whole street just started to run, screaming. I saw a woman right next to me screaming for her kids.
"Police were very, very quickly there, police officers with guns, batons, everywhere. Then the whole street started getting pushed back."
Mr Anwar described the scene as "chaos", with everyone in "panic mode".
He added: "Police officers who got there just started screaming at people to move back, move back.
"One of the shopkeepers tried to speak to him. He said he saw five or six people seriously injured on the ground, a van had driven into people.
"And literally within probably 30 seconds, police vans, ambulances, police officers with guns, were piling out and we were being sectioned off and then being pushed rapidly back down Ramblas."
Eyewitness: It was terriyfying
One witness told Sky News: "It was quite terrifying. All of a sudden scores of people ran towards us, hysterical, children hysterical... first of all they said someone had been shot.
"All of a sudden a second wave of people came down the street, we just ran, I lost my husband in the melee. The shops went into lockdown mode."
She added: "We really had no idea what was going on other than that we needed to get ourselves out of there very quickly... there was just hundreds of people running away very quickly."
Another said: "We were just told to run, it must have been quite close because... there was an immediate stampede to run away. We were just a minute away from it."
Local media: Armed men have entered a restaurant
Spanish media is now reporting that armed men entered a restaurant shortly after the attack took place.
Emergency services - close nearby train and metro stations
Catalan emergency services have asked that nearby metro stations be closed. Here are some images of the scene.
Suspected driver 'fled on foot'
The suspected driver has fled the vehicle, according to local police. It remains unclear whether the crash is terror-related.
Reports suggest the crash happened outside a Kosher restaurant
Several victims treated on the ground
In a photograph shown by public broadcaster RTVE, three people were lying on the ground in the street and were apparently being helped by police and others.
Police cordoned off the broad street and shut down its stores
The scene in La Rambla
Las Ramblas is an iconic avenue in the centre of Barcelona, visited by millions of tourists every year
The local police force was said to be evacuating the area including the nearby main square the Plaza de Catalunya. Shops have put up their shutters with shoppers inside, newspaper La Vanguardia reported.