ZAMBOANGA, Philippines -- More than 100 Philippine troops clashed with about two dozen Muslim rebels Sunday on a southern island where American forces are training soldiers as part of the U.S. campaign against terrorism, officials said.

At least one militiaman fighting with the soldiers was slightly injured in a running gun battle that erupted at dawn and dragged on through the day in coconut groves on Basilan island, said Col. Alexander Aleo, a brigade commander with the Philippine army.

Twelve American advisers who were staying in an army camp in the nearby town of Tipo Tipo were not allowed to venture near the fighting about four miles away and were not in danger, Aleo said.

The rebels belonged to the separatist Moro Islamic Liberation Front, Aleo said. He said the group has given shelter and food to members of a smaller Muslim extremist group, the Abu Sayyaf, which has been linked to the al-Qaida terrorist network and has been holding an Kansas missionary couple and a Philippine nurse hostage since last year.

Thousands of soldiers are pursuing about 60 Abu Sayyaf guerrillas, the remnants of a force that has shrunk since the military launched a massive offensive on the island last June. About 660 U.S. troops are training Philippine soldiers to boost their campaign against the rebels but are not taking part in combat.

FBI Director Robert Mueller, on a six-nation tour of Southeast Asia to discuss cooperation in fighting terrorism, arrived in the Philippines on Sunday to meet with top officials and assess the training mission.

On Friday night, two U.S. Pave Hawk helicopters manned by an American crew evacuated three wounded Filipino soldiers and a dead comrade after they clashed with Abu Sayyaf fighters. The American helicopters were responding to an evacuation request by the Philippine army, which is not equipped for operations requiring night-vision capability.

Aleo said the rescue boosted the morale of his troops.

"The troops at least feel that evacuation is now possible at night and wounded ones don't have to wait for the first light of day," he said. "That's enhancing their confidence."

The training exercise is scheduled to end July 15. U.S. military officials are considering bringing in more soldiers to participate in training and to help improve infrastructure on impoverished Basilan.