The German public television station first reported on the video, which is being attributed to Islamic Jihad Union, a radical group active in Afghanistan and Pakistan.

In the video, which features details of dead children and injured people, six men threaten violence against Germany.

"We have a few surprise packages prepared this year," the men reportedly say. "Allies of the occupation powers must always reckon with our attacks."

Germany currently has 3,600 troops in Afghanistan as part of the International Security Assistance Force (ISAF) in that country.

The video also made reference to the latest conflict between Israelis and Palestinians and to German Chancellor Angela Merkel.

"For 10 days the world has watched as Muslims in the Gaza Strip have been massacred," the men in the video reportedly say. "Where is the US? Where is Mrs. Merkel and her cabinet?"

Germany Federal Criminal Investigations Office confirmed to DPA news agency that it was studying a terror video. Two weeks ago, German authorities found a similar Internet video, in which a man, later identified as a Moroccan-born German national, issued Islamist threats against the country.

Embassy bombing arrest

Meanwhile, in Afghanistan itself, a NATO spokesperson said ISAF has apprehended Sar Gul, one of the alleged masterminds behind the Jan. 17 bombing near the German embassy in Kabul.

The spokesperson said a further suspect in that attack, Mullah Saher, had been killed. The announcement came after ISAF said it had killed "a high-ranking rebel leader" late last week.

Since the fall of the Taliban in 2001, the German army, the Bundeswehr, has mostly been involved in peacekeeping and reconstruction activities in the relatively non-violent north of the country.

But new US President Barack Obama has repeatedly stressed his intention to shift the focus of the struggle against terrorism to Afghanistan and has said he expects America's allies to step up their involvement there.