Five people have been wounded after an axe-wielding attacker went on a rampage in Düsseldorf train station in Germany.
Police said one suspect has been arrested following the attack, but it is not known whether more attackers are on the run.
Swarms of anti-terror police sealed off the German city's main train station following the attack at around 9pm (8pm UK time).
Around five people were injured but it is not known how serious their injuries are.
Police spokesman Rainer Kerstiens initially said more suspected attackers were believed to be on the run and officers are continuing to search the station.
The man who was arrested was also hurt, Düsseldorf police spokewoman Anja Kynast said.
Photos on social media show a person lying on the floor as police tape and officers cordon off part of the stations.
A video recorded from the station concourse shows what appears to be blood on the ground.
Witnesses described how the station was evacuated during the attack.
A worker at the station told German newspaper Bild that a man jumped off a train before attacking people.
They said: "We were standing on the track, waiting for the train. The train came, and suddenly someone jumped out with an axe, hit the people.
"There was blood everywhere."
Another witness, Bruno Macedo tweeted: "Stay away from Düsseldorf train station crazy man with axe on the lose [sic]."
He added: "I am in the train, things look bad."
Sitting in a train at Düsseldorf main station. Whole station was evacuated. Armed police force are searching for a axe murderer. WTF.— Joel Gerhold (@jgerhold) March 9, 2017
Trains were reportedly not stopping at the station while the attack took place.
News reporter Fidelius Schmid from Der Spiegel newspaper said helicopters were circulating overhead and people were crying.
At around 8.30pm, around half an hour after the attack began, he said the station was calmer.
It is not yet clear what the motive for the attack is and police have released no details as to the suspect's identity.
The Bild reported that Düsseldorf mayor, Thomas Geisel, also attended the scene and said: "This is a heavy blow for Düsseldorf. Many eyewitnesses are in shock.
"I am here to thank the police and the rescue team.
"My thoughts are with the victims and relatives."
Germany's chief of staff of the Chancellery, Peter Altmaier, tweeted: "What happened at the Düsseldorf Central Station: our sympathy and our thoughts are with the innocent injured."
Germany suffered a terror attack in Berlin in December last year when a lorry ploughed into a Christmas market, killing 12 and injuring 56.