The bin Laden tape follows two video threats against Germany for its role in Afghanistan earlier this week and came just hours after a third German-language tape by a militant calling himself Abu Talha al-Almani, "The German", alias Bekkay Harrach, who has threatened a "rude awakening" for Germany.

The latest bin Laden message did not threaten new attacks and contained no mention of Germany, except to note that thanks to the financial crisis, "the heart of Europe is no longer number one in world exports". But the use of subtitles to address a German audience so close to Sunday's general election appeared calculated to provoke public unease.

Germany has 4,200 troops in Afghanistan, a deployment that is highly unpopular with the electorate.

The bin Laden audio recording, titled "A message to the people of Europe", lashed out at what it called "the injustices" committed by foreign troops in Afghanistan.

Three videos in a week single out Germany

By contrast, the third, and most recent, video, also released on Friday, was aimed specifically at Germany, and said "because of your commitment against Islam, attacking Germany has become an attractive idea for us, the mujahedeen."

Photographs of famous German sites and events then appear, including the Brandenburg Gate in Berlin, Munich's Oktoberfest beer festival and Cologne's imposing gothic cathedral. Politicians, including Interior Minister Wolfgang Schaeuble and Defense Minister Franz Josef Jung are also shown.

A German crime investigator told Deutsche Welle that the threat was the most concrete so far due to the people and places mentioned. He added that there was concern that the spate of messages could signal an attack was indeed being planned.

Man arrested for posting video

The latest flurry of Islamist propaganda comes as police announced the arrest of a Turkish man suspected of posting the bin Laden video.

The 25-year-old suspect is known to authorities as a supporter of Islamist activists and is said to have been under police observation.

Police from Germany's southern city of Stuttgart, where the arrest was made, say the man is not thought to have taken part in producing the internet video that threatens Germany ahead of the country's national elections on Sunday.

"In searching his apartment, investigators secured numerous items of evidence. The unemployed suspect, who lived alone, was apparently intensely active on notorious Internet platforms,” the police statement said.

The German government has played down a travel alert issued by the US State Department on Wednesday warning American citizens in Germany to be vigilant.

German officials have heightened security in public spaces and train stations as a precaution. Germany, so far, has not been the target of a major attack by Islamist militants.

In 2004, Islamist militants bombed a Madrid commuter train, killing 191 people three days before a Spanish general election.

gb/AFP/AP(/Reuters/dpa
Editor: Andreas Illmer