The four underwent training on sniper courses, night fighting as well as counter-terrorist tactics given by a Special Forces mission in the southern Philippines last year, said a senior official, who asked not to be named.

The mission was part of US military assistance to the Philippines, a key ally in Washington's global anti-terror campaign.

The senior official identified the four US-trained armymen as Captain Gerardo Gambala of the 32nd Infantry Battalion, Captain Albert Baloloy and First Lieutenant Jose Enrico Demetrio Dingle of the Scout Ranger Battalion, and First Lieutenant Laurence San Juan of the Light Reaction Company.

They later used the expertise gained in the training to fight Abu Sayyaf Muslim guerrillas on Basilan island, the source said.

The four have been detained amid court-martial proceedings initiated against the 296 officers and men accused of taking over part of the Makati financial district in the bloodless rebellion on Sunday.

The rising collapsed in 22 hours after they failed to muster civilian and military support to their demands that President Gloria Arroyo and Defense Secretary Angelo Reyes resign over alleged corruption.

WAR.WIRE