Germany was hit by a sharp rise last year in political extremist violence.
The country’s domestic intelligence agency reported that radial groups of the far right, far left and Islamist all gained members.
The security agency had “observed not just a rise in membership but also an increase in violence and brutality,” interior minister Thomas de Maiziere said in a statement.
Last year, 1,408 acts of far-right violence were recorded, against 990 the previous year.
There were 75 arson attacks against refugee shelters in Germany, five times more than 2014.
The report said that online “social networks play an important role in agitation and radicalisation”, as uninhibited hate speech dehumanises minorities and fuels violent crime.
“The intensity of right-wing extremist militancy started in early 2015 and increased steadily – from threats against politicians and journalists to arson attacks on asylum-seeker shelters, and attempted killings,” the report found.
Far-left acts of violence – often targeting far-right activists or police – also went up sharply to 1,608 violent offences from 995 the previous year, said the report.
The service also pointed to the rising threat posed by Islamists, estimating their number at about 10,000.
The report said it assumed that some jihadists and war criminals had entered the country with the massive refugee influx.
Other potential threats were posed by "self-radicalised" individuals, jihadist fighters returned from Syria and Iraq, and possible sleeper cells from militant groups, it said.
