Radical Salafists may be attempting to recruit refugees into their ranks under the guise of offering humanitarian assistance, according to German intelligence officers.

German domestic intelligence agency the Office for the Protection of the Constitution (BfV) said that the number of radical Salafists in the country had risen to 7,900, from the 7,500 recorded in June, and that some may be trying to recruit new members from the tens of thousands of refugees arriving in Germany.

"We are very concerned that Islamists in Germany are trying, under the cover of humanitarian assistance, to exploit the situation of the refugees for their own ends and to proselytise and recruit among asylum seekers," BfV president Hans-Georg Maassen said in a statement.

Previously, radical Salafists have been implicated in terror plots in Germany.

Berlin police earlier reported they had conducted a series of raids targeting people suspected of inciting others to join the jihadist group Islamic State (Isis).

The raids in the early hours of 22 September targeted the properties of a 51-year-old Moroccan man and a 19-year-old Macedonian currently believed to be in Syria, who are believed to part of a recruitment network for the jihadist group. No arrests were made in the raids.

The German government expects 800,000 refugees and migrants to arrive in the country this year, with many fleeing conflict and poverty in the Middle East and Africa.

Maassen said last week that neither his agency nor the foreign intelligence-focussed BND had uncovered any evidence of IS militants entering Europe disguised as refugees. He said that the routes taken by refugees were too perilous to be risked by IS jihadists.