A terror suspect wearing a fake suicide vest has been shot dead by police on London Bridge after he stabbed "a number" of people in central London.
This is what we know so far.
What have police said?
Neil Basu, the head of UK counter-terrorism policing, said: "At approximately 2pm today, police were called to a stabbing at a premises near London Bridge.
"Emergency services attended including officers from the City of London Police and Metropolitan Police.
"A male suspect was shot by specialist armed officers from City of London police and I can confirm that this suspect died at the scene."
Mr Basu said that specialist officers had been deployed after reports that the suspect had an explosive vest, but the device was believed to be a "hoax".
He added: "Due to reports that the suspect might have had an explosive device specialist officers attended the scene.
"However, I can confirm at this time we believe a device that was strapped to the body of the suspect is a hoax explosive device."
Mr Basu said he would give updates to the families of those injured "as soon as we can get that information".
"A number of other people received injuries during this incident. As soon as we can provide further updates on their condition, we will," he told the press conference.
"Our heartfelt sympathies go out to everybody who has been involved in this and is anxiously waiting for information on their loved ones.
"As soon as we can get that information, we will get it to you."
Mr Basu said the attack had been declared a terrorist incident but the force was retaining an open mind to the motive.
He added: "Due to the nature of the incident we responded as though this was terrorist-related.
"I am now in a position to declare it is a terrorist incident.
"Officers from the Met counter terrorism command are now leading this investigation."
Where was the attack?
The suspect was contained and shot on the north side of London Bridge, next to the Fishmongers Hall.
What has London mayor Sadiq Khan said?
In a statement outside Scotland Yard, Sadiq Khan thanked members of the public who risked "their own safety this afternoon".
"I want to thank our brave emergency services who responded to today's horrific attack," the mayor told a press conference at Scotland Yard.
"Every day, they put their lives on the line for us, running towards danger in order to keep us safe.
"I'd also like to thank members of the public who risked their own safety this afternoon. They are the best of us."
Mr Khan asked all Londoners to remain vigilant and report anything suspicious to the police.
What has prime minister Boris Johnson said?
Prime Minister Boris Johnson tweeted: "I want to thank the emergency services and members of the public for their immense bravery in responding to this suspected terrorist attack at London Bridge. This is an appalling incident and all my thoughts are with the victims and their families."
He was returning to London from his home constituency.
What have witnesses said?
Some witnesses reported seeing what appeared to be a "fight" breaking out on the bridge, as a steady stream of people ran from the scene amid shouts from police officers to "keep moving" and a wave of emergency services vehicles raced into the area.
The entire bridge was cordoned off, nearby offices were put on lock-down with staff prevented from entering or leaving, and some businesses were evacuated.
Footage posted from inside a passing bus showed armed police pointing guns at a person who appeared to be lying still on the pavement.
Onlooker Zack Shooter said police almost knocked him over as they ran towards the incident.
"Then loads of cars with sirens all rushed past me at full speed," he added.
In another video filmed from a nearby bus, passengers could be heard gasping in shock as they watched the apparent suspect being shot as he lay on the ground after another man ran from him, having retrieved a large knife.
Some could be heard screaming after more shots were heard, with someone shouting: "They've killed him."
Nurse Jackie Bensfield, 32, described how she asked to be let off a bus on London Bridge after she heard "five or six" gunshots.
Ms Bensfield, who was on her way home from work, said she exited the bus and "ran like hell" to escape the shots.
Ms Bensfield, who was visibly shaken by the incident, said: "I just ran as fast as I could. Hearing gunshots and running from them is not really a good feeling.
"I was on the bus and there was a lot of traffic, but I remember it stopped. Then all of a sudden I see police officers yelling and people running off the bridge.
"I said 'please let me out, please let me out'. Then I just ran as fast as I could.
"'Pop pop pop,' that's what it sounded like. Unfortunately I know what gunshots sound like."
Connor Allen, who was in his van on the bridge at the time, said: "Everyone just started running, you heard these pops and that was it. We just got out the van and started running."
Luke Redman, a 25-year-old data scientist, was in the Monument pub when police entered.
He said he heard "12 or 15 (gunshots) in about 10 seconds", as he left the pub and ran down an alleyway to escape.
Salih Tasdemir was at Kaplan International College when he saw videos of the attack on social media.
"Then I saw police outside and there was an alarm inside the college," the 17-year-old told the PA news agency.
"Then the police were telling us to leave.
"People were running.
"I was really scared."