Berlin, Sep 26 (IANS/EFE): German intelligence estimates put at 450 the number of Islamic State (IS) supporters who have left Germany to travel to either Syria or Iraq to join the jihadis.

Hans-Georg Maassen, who heads the German Federal Office for the Protection of the Constitution, Germany's domestic intelligence agency, revealed the numbers Thursday in remarks to the news channel N24.

Recent estimates had said the number of extremists possessing German passports and suspected of having joined the ranks of IS was 400. It is also thought that 120 of them had subsequently returned to Germany after receiving training at IS camps.

"Aspiring militants were trained to use weapons and explosives, as well as exposed to the radical IS ideology, thereby posing a danger to Germany's security," said Jorg Ziercke, head of the German Federal Police, in remarks to Cicero magazine.

The German interior ministry also warned of the threat to national security represented by returning jihadis, despite there being no clear signs that they planned to carry out attacks.

Maassen warned days ago of the increased use of smartphone apps, including Whatsapp and Instagram, to recruit new jihadis.

He also added that the extremists' return to Germany posed a grave peril for the country, as they could conceivably carry out terrorist attacks or recruit new jihadis to the IS's cause.