Police in Germany on Tuesday have been searching dozens of locations across Berlin looking for more clues after last year's Christmas market attack.
Tunisian Anis Amri (24), killed 12 people when he ploughed a stolen truck into a crowded market.
He was shot dead by Italian police in a Milan neighbourhood, where had fled four days after the Berlin attack.
Security forces focused their raids on about 20 locations, including a mosque believed to have been visited by the attacker.
The mosque, according to authorities, is believed to be part of the radical Salafist scene in Berlin.
Authorities also believe the controversial mosque is a place which supports both terrorism in Syria and raises funds to potentially send people there.
Daesh released a video purportedly showing Amri pledging allegiance to the terrorist group.
TRT World's Ira Spitzer has been following the major police operation in Berlin.