Police have conducted raids across Germany in the early hours in search of suspects involved in plotting a "serious crime against the state," officials say.
Investigators suspect an unspecified number of men from Chechnya, aged between 23 and 28, of scoping out several locations across Germany for what could have been Islamist attack, a joint statement from Berlin police and the city's attorney general's office said.
One of them had been found with suspicious pictures on his mobile phone during a police check, it added.
The raids, which took place in the capital early on Tuesday, the surrounding state of Brandenburg, as well as in North Rhine Westphalia and Thuringia, were conducted in a bid to find more information on the motive.
Police seized cash and sharp weapons as well as hard drives during the raids, in which 180 officers took part.
The statement from the Berlin authorities, which led the operation, said they found "no concrete threat of an attack" according to its most current findings.