About 20 minutes after the hearing opened under tight security at the Beirut criminal court, Judge Michel Abu Arraj decided to adjourn the hearing until May 10.

The defense argued at the opening of trial a week ago that the Beirut court was not entitled to try four suspects in Lebanese custody, insisting that they should be tried in northern Lebanon where they live and where they were arrested on Sept. 4.

The four men in the dock are suspected mastermind Jihad Hamad, 22, as well as Khaled al-Hajj Dib, 19, Ayman Hawwa, 22, and Khalil Bubu, 23, judicial sources said.

Bubu is also facing another trial for links in a bomb attack on a Lebanese army barracks in Beirut last year.

Suspects targeted German passengers

At the opening of the trial last Wednesday, the Beirut court also issued arrest warrants for Saddam al-Hajj Dib, who remains at large, and his brother Yusef Mohammed al-Hajj Dib, who is in custody in Germany. Both are being tried in absentia.

While Yusef Mohammed al-Hajj Dib is being detained on a German arrest warrant, the court in Beirut decided to issue a Lebanese arrest warrant.

All six are being tried for "an attempt to carry out mass killing in two passenger trains in Germany on July 31 by using incendiary materials confiscated by German authorities," a judicial source said.

If found guilty, the four suspects in custody could be jailed for a maximum period of 15 years while those in absentia could receive longer prison terms.

Suspect: Plot linked to Mohammed cartoons

Hamad has confessed under judicial interrogation to having placed a suitcase containing explosives on a train in Germany last July, Lebanese judicial sources said.

"The intention was not to kill people, but to avenge any harm done to Muslims after the publication in Denmark of cartoons that were harmful to the Prophet Mohammed," Hamad was quoted as saying.

German federal police said the publication of cartoons of the Prophet Mohammed in Western and some Arab media had been the "detonator" which pushed the gang to organise a plot to bomb German trains on July 31.

The plan failed when bombs concealed on two regional trains did not explode because of faulty detonators.

German newspaper Süddeutsche Zeitung said last week that bomb-building instructions had been found on a deleted hard disk of a laptop computer which Hamad had taken with him from Germany to Lebanon.