Manila, Philippines ? Philippine troops, backed by helicopter gunships, pounded Muslim extremist guerrillas with artillery and rocket fire Monday in the latest clash in a U.S.-backed military offensive, officials said.

At least one soldier was wounded and an unspecified number of Abu Sayyaf guerrillas were killed or injured in the mountainous hinterlands of Patikul town on Jolo island, the military said.

The guerrillas were dragging away their wounded or dead, making it hard to estimate their casualties, military spokesman Lt. Col. Danilo Servando said.

Maj. Gen. Ernesto Carolina, who heads the southern Philippine military command, said army scout rangers fought the same guerrillas last Thursday, when one army officer was killed and seven soldiers were wounded.

President Gloria Macapagal Arroyo said the military has captured four guerrilla camps in Patikul since Thursday. She described the current offensive as a major attempt to wipe out remnants of the al Qaida-linked group on Jolo island.

The guerrillas, a combined group of Abu Sayyaf led by chieftain Khadaffy Janjalani and Radullan Sahiron, had been tracked by U.S. surveillance aircraft, Carolina said last week.

Janjalani helped lead a raid on a southwestern island resort, where the guerrillas abducted 20 people in May 2001, including three Americans. That raid set off a kidnapping spree that victimized a total of 102 people, 18 of whom were beheaded or hacked to death.

An army rescue attempt on the final three hostages on June 7 left American missionary Martin Burnham and Filipino nurse Ediborah Yap dead. Burnham’s wife, Gracia, was wounded but survived.