A Moroccan arrested in Belgrade on suspicion of involvement in the March 2004 Madrid train bombings remained in detention in Serbia Thursday, pending his extradition to Spain.

Belgrade is now waiting for a formal extradition request from Spanish authorities but the suspect, identified as 22-year-old Abdelmajid Bouchar, could be detained in Serbia for up to a year, said the country's Human Rights Minister Rasim Ljajic.

"The (extradition) procedure will certainly last several weeks, possibly a few months," Ljajic said.

Bouchar will be allowed to appeal against a possible extradition decision, while Ljajic, as human rights minister, has the final say regarding extraditions.

Spain, which had issued an international arrest warrant against Bouchar, said it would seek his extradition as soon as possible. He is one of more than 70 suspects waiting to stand trial for the attacks.

The Serbian Interior Ministry said police arrested Bouchar during a routine check of documents on a train. He was caught travelling from Subotica, on Serbia's border with Hungary, to Belgrade without any identification.

The Serbian interior ministry did not say when Bouchar was arrested, only that the Spanish Interpol bureau identified his fingerprints.

Bouchar is suspected of helping to plant the bombs on Madrid commuter trains as well as performing services such as acquiring a car for the terrorists. The bombings, Spain's worst terrorist attacks, killed 191 people.

Just three weeks after the bombings, Bouchar was almost caught when police surrounded an apartment he was staying at with other suspects in Leganes near Madrid. However, he spotted police circling the building and fled.