DÜSSELDORF, Germany — An axe-wielding attacker suffering from mental health problems injured seven people at the main train station in the German city of Dusseldorf late Thursday, police said.

Previously police had said several attackers were involved and two were arrested but they later said one suspect was behind the assault, a 36-year-old man from the former Yugoslavia.

"An assailant probably armed with an axe attacked people at random" at about 8.50pm local time (1950 GMT), city police said in a statement.

Police initially gave the number of injured as five, but updated that to seven in a later statement.

While trying to escape the man jumped from a bridge and suffered serious injuries from the fall, the statement said. He was not in a position to be interrogated, German news agency DPA reported.

Large numbers of police, including special units, were deployed at the station and traffic was halted. Bild newspaper reported that helicopters flew overhead.

"Interruption at the central station in Dusseldorf. We can’t say when the trains will start running again," regional police said on Twitter.

"We were on the platform waiting for the train. The train arrived and suddenly someone with an axe came out and started attacking people," an unnamed witness told Bild.

"There was blood everywhere," the witness was quoted as saying.

Peter Altmaier, a close adviser to Angela Merkel, wrote on Twitter: "What happened at the central station in Dusseldorf, our compassion and our thoughts go out to the injured."

Thomas Geisel, city mayor, also reached out to victims, according to Bild. "It’s a huge blow for Dusseldorf. Many people are in shock. I’d like to thank the police. My thoughts go out to the victims and their families," he said.

German authorities have been on alert for terror attacks, especially since an assault claimed by the Islamic State group in December when a hijacked truck ploughed into a Berlin Christmas market, killing 12 people.

According to German security services, there are about 10,000 radical Islamists in the country, of whom 1,600 have suspected links to terror groups.

There was another axe attack on a train in 2016 in Germany’s Bavaria, but no-one was killed and the attacker was found to be mentally unbalanced. — AFP