The suspect believed to be the driver who ploughed a lorry into a Christmas market in Berlin has denied involvement in the attack, Interior Minister Thomas de Maiziere said Tuesday.

"He denies the act," de Maiziere told journalists, adding that the suspect is Pakistani and had arrived in Germany on December 31, 2015, seeking asylum.

His request was still pending, the minister said, adding that Monday's bloodshed had so far not been claimed by the Islamic State organisation or any other group.

De Maiziere said however: "We have no doubt that this terrible event was an attack."

READ: 12 killed as lorry ploughs into Berlin Xmas market

Twelve people were killed in the assault at a shopping district popular with tourists, and 48 people injured, including 18 who are severely wounded.

Christmas markets in Berlin were shut for a day out of respect for victims and their relatives, but de Maiziere said the markets or major events elsewhere must continue.

"Cancelling them would be wrong," he said.