There is no concrete information about a specific area or establishment

BKA

The country's federal office for criminal investigations, the BKA, which issued the warning, insisted however that it did not know of a specific date or target for the attack, or how it might be carried out.

But it did say that US, Jewish and British sites in the country were seen as being particularly threatened.

The confirmation that warning letters had been sent to state security bodies followed an article in the daily Frankfurter Allgemeine Zeitung (FAZ), which reported that a member of the al-Qaeda terrorist network had developed a plan to take 300 to 400 hostages in Germany, France and Britain.

Churches and cinemas

According to FAZ, which claimed to be citing a leaked BKA report, the hostages would be taken in churches or cinemas in those three countries.

Demands for the release of al-Qaeda prisoners in exchange for freedom for the hostages would then be issued to the authorities. Dozens of alleged members of the terrorist network are currently being held by the United States.

If these requests were not met, the extremists would then blow themselves and their captives up.

The Frankfurt paper added that German police are now looking for three men in connection with the alleged plot, named only as Schah Ahmad Pergham, Raschid and Nisa.

Germany has kept a close watch on extremist activity since it emerged that three of the suicide hijackers who carried out the 11 September terrorist attacks on New York and Washington had lived in the northern city of Hamburg.

Last week, German magistrates remanded in custody nine men suspected of belonging to a militant Islamic group, eight of whom are accused of plotting to carry out attacks on civilian targets in the country.

Germany further stepped up security precautions after an explosion at a synagogue in Tunisia earlier this month, which killed 11 German tourists.

German and Tunisian authorities are agreed that the incident was a terrorist attack.