ZAMBOANGA, The Philippines -- An Abu Sayyaf leader has been captured and four members of the Muslim rebel group killed in the southern Philippines, where U.S. and Philippine troops are conducting joint operations, officials said Monday.

Military intelligence operatives arrested Abu Sayyaf Commander Sonny Ping on Saturday on Basilan, an island stronghold of the guerrillas where the joint operations are focused.

Villagers tipped off the authorities on Ping as he conducted "surveillance operations" on possible U.S. and Filipino military targets in the town of Lamitan, army brigade chief Colonel Alexander Aleo told AFP.

"He is currently being investigated and interrogated," Aleo said.

Ping has a one million-peso (19,600-dollar) bounty on his head.

The military said he is an aide to Abu Sayyaf Leader Abu Sabaya, who has reportedly fallen ill amid a massive pursuit operation.

Meanwhile, an army soldier was wounded and four Abu Sayyaf rebels were killed in separate clashes in Basilan and nearby Jolo island, the military said.

Military southern command Captain Noel Detoyato said a soldier was wounded Sunday in a 15-minute firefight with the rebels in Basilan's Tuburan town, where U.S. special forces are deployed with a local army contingent.

"There were no U.S. special forces present in the encounter since they are still in the Batallion headquarters acquainting themselves with soldiers and local officials in the area," Detoyato said.

Late on the same day, members of the Philippine army's elite special forces were attacked by some 20 Abu Sayyaf guerrillas while patrolling a rebel stronghold in Jolo's Maimbung town.

Four of the gunmen were slain in the 30-minute firefight that ensued, said Jolo army chief Colonel Romeo Tolentino.

Some 160 U.S. Green Berets are deployed in Basilan to train the local military in fighting the Abu Sayyaf, a small group of Islamic militants holding captive U.S. Christian Missionary couple Martin and Gracia Burnham and a Filipina nurse.

The U.S. and Philippine governments have linked the Abu Sayyaf to the Al-Qaeda terror network of Osama bin Laden, the alleged mastermind of the September 11 attacks in the United States.