Twelve people were killed and at least 50 more injured after an articulated lorry ploughed into a busy Christmas market.
According to the German DPA news agency, at 20:14 local time (19:14 GMT), the lorry sped around 50-80 metres through the market at Breitscheidplatz, close to the Kurfuerstendamm, the main shopping street in the heart of western Berlin.
The driver of the lorry was arrested at the scene and a Polish co-driver was found dead in the vehicle, according to police.
The lorry is believed to be registered in neighbouring Poland, and Polish media have suggested it may have been stolen earlier on Monday.
Berlin State Interior Minister Andreas Geisel said “the sequence of events points to either an accident or an attack”, but eyewitnesses describe a deliberate act in the same vein as the Islamic State’s Bastille Day attack in Nice of 14 July.
In a statement, German President Joachim Gauck said it was an “awful evening for Berlin and for our country”.
German authorities have appealed for the public to avoid the Breitscheidplatz area of Berlin and set up a emergency information phone number for those concerned about loved ones to call: +49 30 54023 111. Facebook also setup a “Safety check” page for those nearby the attack to inform loved ones they are safe.