Tunisian-born Anis Amri traveled to 15 different mosques - 12 of which were located in the western Ruhr region, according to a report from German public broadcaster WDR's "Aktuelle Stunde" television program.

Amri used one of eight aliases to apply for asylum in the western German city of Oberhausen, the report said citing a multi-page profile on the Berlin attack suspect put together by security authorities.

Starting in February 2016, Amri was located mostly in Berlin although he should not have been allowed to leave the state of North Rhine-Westphalia, where he registered for asylum.

The state criminal investigation office in Düsseldorf classified him as a threat on May 10.

The profile stated that Amri behaved in an especially conspiratorial manner when he was in Berlin and had frequent contact with people who security services said had ties to the radical Salafist-Islamist scene. Two of the men Amri came into contact with were under suspicion of planning a terrorist attack.

Back in North Rhine-Westphalia, Amri also had two contacts in Dortmund who had ties to the so-called militant "Islamic State" (IS) group, the report said.

On October 13, 2016, surveillance information gathered by state-level security authorities was supposed to be passed on to Germany's domestic intelligence agency, the Federal Office for the Protection of the Constitution (BfV), WDR's "Aktuelle Stunde" reported. Domestic intelligence work in Germany is generally conducted by authorities in the country's 16 states.

Revelations that Amri had been on a federal list of persons regarded as a potential threat and had been monitored by authorities for months has prompted sharp criticism toward security failures in Germany.

Amri is suspected of driving a truck into a crowded Berlin Christmas market last Monday, killing 12 people and wounding 48 others.

IS claimed responsibility for the Berlin attack, while German authorities are investigating to what extent Amri may have received support before or after the assault.