German prosecutors have issued an arrest warrant for Saifi

German authorities have announced that Ammari Saifi - known as Abderrezak - was captured along with another man.

But they said the circumstances of his arrest "still have to be clarified".

He allegedly leads the Salafist Group for Preaching and Combat (GSPC), which is blamed for abducting the tourists, many of them Germans, in 2003.

On Friday, a Chadian rebel group, the Movement for Democracy and Justice in Chad (MDJC), said it had been holding Mr Saifi since mid-March.

"We have given the description of each prisoner to the Algerians and they recognised him," Reuters news agency quoted an Paris-based MDJC spokesman as saying.

"Initially he gave us all sorts of weird names, but eventually he admitted his identity."

Arrest warrant

Since September 2003, Mr Saifi has been the subject of an international arrest warrant issued by Germany.

The warrant accuses him of kidnapping, extortion, membership in a foreign terrorist organisation and attempted blackmail of the German government.

Germany is reported to have paid a ransom for the hostages, but the government has refused to confirm or deny this.

The tourists were captured in small groups during a spate of kidnappings in the Sahara desert.

All but one of the hostages - a German woman who died of heat stroke - were freed.