Updated

Germany faces a growing threat from militant Islamists and far-right fringe groups, including small extremist cells and lone wolf operators, top security officials said Wednesday.

A report by Germany's domestic intelligence agency puts the number of Salafi Muslims in the country at 3,800 last year, with a small number of those prepared to use violence to achieve their aims. It is the first time the agency has counted the number of German-based Salafists, a religious movement that adheres to a strict interpretation of Islam and which has attracted young Muslims as well as recent converts.

The wider number of Muslims with extremist views is estimated at more than 38,000, according to the report.

"Our focus remains on Islamist terrorism," Heinz Fromm, the head of the Federal Office for the Protection of the Constitution, told reporters in Berlin. "This is where the main threat currently comes from."

Fromm cited the killing of two U.S. airmen at Frankfurt airport last year as an example of the acute but unpredictable nature of Islamist-inspired extremism.

Arid Uka, 22, was convicted in February of murder and sentenced to life in prison. Prosecutors said Uka, an ethnic Albanian born in Kosovo who grew up in Germany, became radicalized on his own by reading and watching jihadist propaganda on the Internet.

"In the coming years the intelligence work of the security agencies will continue to be dominated to a large degree by the problem of individual jihadists," Fromm said.

His agency's annual report also noted an increasing number of members of militant far-right groups. Authorities were deeply embarrassed last year by the revelation that a small group of neo-Nazis apparently managed to commit as many as 10 murders over a seven-year period while remaining largely off the radar of the intelligence services.

The existence of the National Socialist Underground only came to light last November, when two of its three core members were found dead in an apparent murder-suicide after a failed bank robbery. The third alleged core member, Beate Zschaepe, is in custody pending trial.

The NSU murders, as well as subsequent revelations that one of Fromm's agents had shredded files linked to the case, prompted him to resign earlier this month. He retires at the end of the month.

The government on Wednesday appointed Interior Ministry official Hans-Georg Maassen as Fromm's successor.

Officials estimate that the wider membership of neo-Nazi groups in Germany fell to 22,400 from 25,000 in 2010, but the number of far-right extremists prepared to use violence grew last year to 9,800 from 9,500.

German Interior Minister Hans-Peter Friedrich said authorities were on alert for possible attacks by neo-Nazis inspired by the NSU killings.

"I see that the potential, in particular for copycat acts, is present," Friedrich said.

Federal police say at least seven wanted neo-Nazis are currently on the run in Germany.

Recent left-wing extremism in Germany has been largely restricted to outbursts of violence during street protests, and acts of sabotage. The number of left-wing extremists in Germany fell by 400 to 31,800 last year, according to the report. It counted 7,100 violent left-wing extremists, up from 6,800 in 2010.