At least five people were killed and more than 200 injured in a car-ramming attack at a Christmas market in the German city of Magdeburg, officials said, and a Saudi man was arrested on suspicion of driving into the crowd.
The Friday evening attack on the market comes amid a fierce debate over security and migration during an election campaign in Germany, where the far right is polling strongly.
"What a terrible act it is to injure and kill so many people ... with such brutality," Chancellor Olaf Scholz said as he laid a white rose in honour of the victims at a church in the city.
"We have now learnt that over 200 people have been injured," he added. "Almost 40 are so seriously injured that we must be very worried about them."
German authorities are investigating a 50-year-old Saudi doctor who has lived in Germany for almost two decades in connection with the attack. Police searched his home overnight.
The motive remained unclear and police have not yet named the suspect, although he has been named in German media as Taleb A.
A Saudi source told Reuters that Saudi Arabia had warned German authorities about the attacker after he posted extremist views on his personal X account that threatened peace and security.
Der Spiegel reported that the suspect had sympathised with the far-right Alternative for Germany (AfD) party. It did not say where it got the information.
Germany's domestic intelligence agency declined to comment on the ongoing investigation.
The Saudi suspect is considered to hold "Islamophobic" views, Interior Minister Nancy Faeser said on Saturday. She said that while she did not want to speculate about the motive, "the one thing" she could confirm was that he had expressed an "Islamophobic" stance.
Germany's Frankfurter Allgemeine Zeitung newspaper said it interviewed the suspect in 2019, describing him as an anti-Islam activist.
"People like me, who have an Islamic background but are no longer believers, are met with neither understanding nor tolerance by Muslims here," he was quoted as saying. "I am history's most aggressive critic of Islam. If you don't believe me, ask the Arabs."
Magdeburg, 130km south-west of Berlin, is the state capital of Saxony-Anhalt and has about 240,000 residents.
German President Frank-Walter Steinmeier said that "the anticipation of a peaceful Christmas was suddenly interrupted" by the tragedy. French President Emmanuel Macron said he was "profoundly shocked" and he "shares the pain of the German people".
But the leader of the far-right anti-immigrant Alternative for Germany, Alice Weidel, wrote on X: "When will this madness stop?"
Eight years ago a Christmas market in Berlin was attacked. On December 19, 2016, an Islamist extremist ploughed through the crowded market with a lorry, killing 13 and injuring dozens more. The attacker was killed days later in a shoot-out in Italy.
German Interior Minister Nancy Faeser said late last month that there were no concrete indications of a danger to Christmas markets this year, but that it was wise to be vigilant.
