Police have searched dozens of sites in Germany linked to a mosque that was frequented by Berlin market attacker Anis Amri, after authorities banned the Islamic group that operated the prayer house.
Some 450 officers raided 24 locations in Berlin, the neighbouring state of Brandenburg and Hamburg in northern Germany, starting at 6am local time (5am Irish Time).
In addition to the mosque itself, they searched 15 apartments, two company offices and six prison cells. No arrests were made.
Senior security officials said authorities had been watching the mosque for some time because of concern that it had become a meeting point for Islamic extremists.
An attempt to ban the organisation behind it, known as Fussilet 33, was aborted last summer.
That decision was heavily criticised months later when it transpired that Amri had visited the mosque only an hour before driving a truck into a crowded Christmas market on December 19, killing 12 people and injuring dozens more.
Amri, a 24-year-old Tunisian citizen, was shot dead by police in Italy four days after the attack.
Berlin's top security official said authorities had seized funds belonging to Fussilet 33, shut down its website and imposed a blanket ban to prevent the organisation from establishing itself under a different name or location.
"It was necessary to ban the organisation and all successor organisations to stop it once and for all," Andreas Geisel told reporters.
"People who preach hate have no place in this city."
Mr Geisel said several prominent members of Fussilet 33 had been arrested in the past on suspicion of supporting extremist organisations such as Islamic State and Jund al-Sham.
Documents and electronic devices seized during Tuesday's raids were being examined to see whether members of the organisation knew of Amri's plans, he said.
"We currently have no indications that any further concrete attacks are planned in Berlin," said Mr Geisel.