German Chancellor Angela Merkel arrives for a news conference in Berlin, Germany, December 20, 2016, one day after a truck ploughed into a crowded Christmas market in the German capital. REUTERS/Hannibal Hanschke

BERLIN (Reuters) - German Chancellor Angela Merkel said on Tuesday she believed the incident at a Christmas market in Berlin which killed 12 people on Monday was a terrorist attack, adding it would be hard to bear if it turned out that a migrant had been the perpetrator.

“There is much we still do not know with sufficient certainty but we must, as things stand now, assume it was a terrorist attack,” Merkel told reporters.

“I know it would be especially hard for us all to bear if it were confirmed that (the) person who committed this act was someone who sought protection and asylum,” she added. She promised that every detail would be cleared up and the perpetrator would be punished with the full force of the law.