BEIRUT, Lebanon: A Lebanese citizen confessed under judicial interrogation Monday to planting one of the bombs used in last year's abortive attempt to blow up two German trains, a judicial official said.

The suspect, Jihad Hamad, told an investigating magistrate that he was trying to avenge the publication of cartoons of the Prophet Muhammad, the official said, speaking on condition of anonymity because he was not authorized to speak to the press.

Lebanon arrested Hamad and three other suspects on charges of planting crude bombs on two trains at Cologne station on July 31. German surveillance cameras are said to have filmed the suspects as they pulled wheeled suitcases in the station.

The bombs were found later that day on trains at Koblenz and Dortmund stations. Their detonators went off but failed to ignite the explosives.

On Monday, police took the four suspects under heavy security from Roumieh prison to the Justice Palace in central Beirut, where they underwent preliminary interrogation by Judge Michel Abu Arraj.

Hamad, who comes from the northern city of Tripoli, told the judge that his aim in planting the bomb was not to kill but to defend Islam, the official said. He said he was retaliating for the publication of 12 cartoons that satirized the Prophet Muhammad.

One of the drawings, which were first published in the Danish newspaper Jyllands-Posten in September 2005, showed Muhammad wearing a turban shaped like a bomb. The cartoons, which were republished in German and other European papers, sparked outrage across the Muslim world, where many consider images of the prophet to be blasphemy.

The head of Germany's Federal Crime Office, Joerg Ziercke, has said that the train-bomb suspects were also motivated by the June 7 killing of al-Qaida in Iraq leader Abu Musab al-Zarqawi in a U.S. airstrike.

No date for the suspects' trial was set Monday. The three other suspects in custody are Ayman Hawa, Khalil al-Boubou and Khaled Khair-Eddin el-Hajdib, whose brother Youssef is under arrest in Germany in connection with the case.

German officials briefly arrested a 23-year-old Syrian, Fadi al-Saleh, on suspicion that he did research on the Internet to prepare the bombings.

Germany wants to extradite the suspects, but there is no extradition treaty between Germany and Lebanon. Lebanon has decided to try the suspects in its courts, as they were arrested on its territory, and defer consideration of extradition until later. -AP