The tourists were travelling without guides

German Chancellor Gerhard Schroeder is reported to have offered special forces to Algeria to help search for 31 European tourists missing in the Sahara desert.

The offer is included in a letter sent last week to Algerian President Abdelaziz Bouteflika, German weekly Der Spiegel says in its Monday edition.

Chancellor Schroeder calls on the Algerian president to do everything he can to find the tourists.

Algeria has deployed thousands of soldiers in a hunt for the 15 Germans, 10 Austrians, four Swiss, a Dutchman and a Swede missing in the desert since February.

The authorities have said they have been kidnapped but by who is the matter of speculation. The Algerian media has speculated the missing tourists may have been kidnapped by the Salafist Group for Preaching and Combat (GSPC), an Islamic militant group fighting the Algerian authorities.

The search operations are nothing but a sordid show aimed at impressing the media Algerian Free Officers' Movement

The group is suspected of having links with Osama bin Laden's militant al Qaeda network.

Another theory, recently aired by an opposition group, is that the Europeans are being held by members of the Algerian intelligence service who aim to embarrass the government.

On its website, a military opposition group, the Algerian Free Officers' Movement, says the tourists are being "held illegally inside a military facility in the south" and that the search operations are nothing "but a sordid show aimed at impressing the media".

The kidnappings were in direct response to changes he has made in the military hierarchy, the group continued.

The Algerian Interior minister Yazid Zerhouni said on Friday he believed the tourists were alive.

The German government has reportedly suggested sending elite GSG9 troops specialised in hostage situations, but only if the use of force cannot be avoided, according to the Berlin daily, Der Tagesspiegel.

Germany has already sent five members of GSG9 and the federal criminal investigation bureau BKA to Algeria to gather information and provide advice.