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.

As a nation mourned, with citizens leaving flowers and lighting candles in Magdeburg where the incident took place on Friday, questions swirled about whether more could have been done and whether the authorities could have acted on warnings.