Berlin, Dec 21 (IANS): The Islamic State (IS) terror group has claimed responsibility for Monday night truck assault at a Berlin Christmas market that killed 12 people.

The IS-affiliated Amaq news agency released a statement late Tuesday saying the attack in which 49 others were also injured, was carried out by "a soldier of the Islamic State" in response to calls by the group's leadership to target citizens of international coalition countries, CNN reported.

According to the BBC, German Interior Minister Thomas De Maiziere reacted cautiously to the claim, saying "several lines of investigation" were being pursued.

Earlier on Tuesday, German prosecutors freed the only suspect, citing insufficient evidence.

He was identified by media only as Pakistani national Naved B.

Officials suggested that a perpetrator or perpetrators may still be on the run.

The sole suspect was captured in a park after reportedly fleeing the scene and being tracked by a member of the public, who alerted the police.

The lorry's original driver, Polish citizen Lukasz Urban, was found dead on the passenger seat, reportedly with gunshot and stab wounds to his body.

No gun was recovered, the BBC added.