Two people have been killed, including a child, and dozens injured after a car drove into a crowd at a Christmas market in the eastern German city of Magdeburg, officials say.
In a statement, authorities said 68 people had been injured, 15 of whom seriously.
Reiner Haseloff, the premier of the state of Saxony-Anhalt, told reporters at the scene that the suspect – who has been arrested – was a 50-year-old Saudi citizen who arrived in Germany in 2006 and had worked as a doctor.
He said a preliminary investigation suggested the alleged attack was acting as a lone wolf and that he could not rule out further deaths due to the number of injured.
Footage from the scene shows numerous emergency services vehicles attending while people lay on the ground.
Unverified video on social media purports to show a car ploughing into the crowd at the market.
A spokesperson for the city of Magdeburg said all hospitals in the area were preparing for a “mass casualty event”, according to the Reuters news agency.
City officials said around 100 firefighters and 50 rescue service personnel are at the scene.
German Chancellor Olaf Scholz said reports from Magdeburg “lead us to fear the worst”.
He added: “My thoughts are with the victims and their loved ones. We stand by their side and by the side of all Magdeburg residents. My thanks to all the emergency services in these difficult hours.”
Scholz will visit the city on Saturday, Haseloff said.
Around 19:20 local time (18:20 GMT), the organisers of the Christmas market announced that it had been closed as asked “for understanding”.
A short while later, they called for members of the public to avoid the market. “Please let the emergency services do their job and leave the market in an orderly manner,” they wrote on social media.
In an interview with German paper Bild, Nadine, described being at the Christmas market with her boyfriend, Marco, when the car came speeding towards them.
“He was hit and pulled away from my side,” the 32-year-old told the paper, saying that she had yet to find Marco. “The uncertainty is unbearable.”
Meanwhile, Lars Frohmüller, a reporter for German public broadcaster MDR, told BBC Radio 4’s World Tonight he saw “blood on the floor” as well as “many doctors trying to keep people warm and help them with their injuries”.
When the incident occurred, Magdeburg’s football team were playing against Fortuna Dusseldorf.
After the game finished, the team’s players united in a line in front of their supporters. A statement from the club said its “thoughts are with those affected by the terrible events and the Magdeburg Christmas market”.
Meanwhile, a minute’s silence was held at the end of a match between Bayern and RB Leipzig in Munich.
Friday’s incident is not the first time people at a Christmas market have been attacked in Germany.
In 2016, Anis Amri, a Tunisian man who failed to gain asylum in Germany and had links to the so-called Islamic State (IS) group, drove a truck into crowds gathered at a church market in Berlin, killing 12 and injuring 49 others.
Two years later, a gunman opened fire on a Christmas market in the eastern French city of Strasbourg, killing five and injuring another 11 people. The gunman was shot dead by police two days later.
French President Emmanuel Macron said his country “shares the pain of the German people and expresses its full solidarity” following the incident in Magdeburg.