German police have been accused of failing to act on warnings about Berlin Christmas market attacker Anis Amri, and covering their tracks after he killed 11 people last December.

Berlin politicians are calling for a full, federal investigation into the Amri case after new documents emerged contradicting police claims that he was viewed as a low level threat.

This low threat status was the justification offered by Berlin’s state criminal police (LKA) for ending undercover observation of him in June, despite concerns of police in western Germany.

According to documents seen by Berlin broadcaster RBB, the LKA considered the Tunisian man a threat for two months after ending the observation.

‘Violent threat’ A report from August 2016 admitted Amri posed a “growing violent threat”, two months after observation had been reduced to monitoring his mobile phone.

On December 19th he hijacked an articulated lorry and drove it into a Christmas market in Berlin’s western city centre, killing 11, before being shot while on the run in Italy.

“I am now convinced the attack could have been prevented. We need a full parliamentary inquiry into the Amri case,” said Hans-Christian Ströbele, a Bundestag MP with the opposition Green Party.

Berlin’s state interior minister Andreas Geisel said he was not aware of the new documents but said they raised questions about the police version of events to date.

Until now police have said their attempts to observe Amri, who came to Germany in 2015, were limited by the lack of evidence of a concrete attack plan. After a failed asylum application Amri stayed on in Germany and, despite contacts to a mosque known for links to the Islamic State terror group, Berlin police assumed he had lost interest in radical Islam last year and had become a petty criminal.

Missed opportunities Meanwhile a separate Amri inquiry in the western state of North Rhine-Westphalia (NRW) has heard that, contrary to official claims, authorities missed opportunities to deport Amri before the attacks.

Until now, NRW interior minister Ralf Jäger said authorities had been unable to deport Amri because he had no identification card or passport; documents allowing him to travel arrived from Tunis two days after the attack.

But federal prosecutor Peter Frank disputed this version of events, telling the NRW parliamentary inquiry on Friday that, in similar cases, it had been possible to detain suspects until their deportation.