Mourners are laying flowers near the scene of the deadly Christmas market attack as investigators puzzle over the motive of the suspect.

Thousands of people in Magdeburg formed a human chain on Monday to remember the victims of the attack on a Christmas market in the central German city, as the far-right Alternative for Germany (AfD) held a rival rally.

Abdulmohsen, a 50-year-old doctor from Saudi Arabia, had expressed anti-Islamic views and described himself as a Saudi dissident, an official said.