Islamic State wants to carry out attacks in Germany and the security situation is "very serious", the head of the country's domestic intelligence agency (BfV) told a Sunday newspaper, adding that he knew of no concrete plot to strike.
The militant group released a video on Tuesday suggesting it may carry out further attacks in the West after the Brussels bombings and Paris attacks, naming London, Berlin and Rome as possible targets.
Hans-Georg Maassen told German newspaper Welt am Sonntag the group wanted to carry out attacks against Germany and German interests, but added: "At the moment we don't have any knowledge of any concrete terrorist attack plans in Germany."
He said Islamic State propaganda was aimed at encouraging supporters to take the initiative to stage attacks in Germany.
Maassen said there were several cases linking Germans returning from Syria to attack plans and warned that the danger posed by militants from Germany remained "virulent".
The newspaper cited a response from the German government to an inquiry from the opposition Greens as saying arrest warrants had been issued for 76 suspected Islamists believed to be prepared to use violence.
Of the more than 800 people security authorities know have travelled to Syria and northern Iraq from Germany in recent years, around 130 have died, it said.
Around a third of the people who have travelled to the region since 2012 are now back in Germany and about 70 of the returnees actively took part in fighting or completed military training, it added.
Maassen said Germany had avoided a big attack so far thanks to the successful work of security agencies and luck such as a bomb detonator not working properly on one or two occasions.
In 2014, a German man described as a radical Islamist was charged with planting a pipe bomb -- which never exploded -- at Bonn train station in 2012. In 2006, two suitcase bombs left by Islamist militants on trains in Cologne failed to explode.
Asked how many Islamists in Germany were considered highly dangerous, Maassen said there were about 1,100 Islamists who were seen as a potential terrorism risk.
Maassen said his agency was aware of about 300 attempts by radical Islamists to recruit refugees.
"I'm particularly concerned about the many unaccompanied minors -- this group is being deliberately targeted," he said, adding that he saw a "huge radicalisation potential" in these attempts to recruit people.
The newspaper also said criminal Arab clans were trying to recruit refugees and quoted Sjors Kamstra, senior public prosecutor in Berlin, as saying: "The refugees come here and have no money and they're being shown how they can get their hands on some money very quickly if they're unskilled."
He said many of the refugees could not speak German so were particularly susceptible to recruitment if someone addressed them in their mother tongue.