A Muslim guerrilla leader whose fighters kidnapped two Kansas missionaries and scores of other people was shot in a clash with U.S.-trained troops Friday and may be dead, President Gloria Macapagal Arroyo said Friday. 

Abu Sabaya, the most visible commander in the extremist Abu Sayyaf, was one of three guerrillas who jumped off a boat after being wounded in a firefight with elite navy troops, Arroyo said. She said four guerrillas were captured. 

"The captured Abu Sayyaf members confirmed that one of those who jumped into the sea was Abu Sabaya, who was wearing a black sweat shirt," the president said. "The [military] team also confirmed shooting the man in the black sweat shirt." 

A military source said a body believed to be that of Sabaya was recovered and officials were trying to confirm the identity. 

"We did get word from the [Philippine military] that Abu Sabaya was one of those killed in the encounter," said Maj. Richard Sater, a spokesman for U.S. forces conducting a counterterrorism training exercise aimed at helping local troops wipe out the Abu Sayyaf. "We are encouraged. It is a step forward in the war against terrorism." 

The Philippine military said it had been hot on Sabaya's trail since two of the group's last three hostages — American Martin Burnham and Filipina Ediborah Yap — were killed during a June 7 clash along with three rebels. Washington recently offered a $5 million bounty for his capture. 

Arroyo, who repeatedly has vowed to crush the Abu Sayyaf, congratulated the military in a written statement, adding: "Terrorists will be hunted down relentlessly wherever they are. They will be given no room to maneuver, to hide, or to rest. We will not stop until they are all accounted for." 

She said the clash occurred around 4:30 a.m. half a mile offshore in Zamboanga del Norte province, site of the June 7 clash. 

Sater said Americans provided unspecified support during the clash but were not directly involved in the fighting. 

"We're here to advise and assist. We helped out in that capacity this morning, providing some surveillance and communication, that sort of thing," Sater said. Asked whether Americans were nearby, Sater said: "Yes, but I can't say how near." 

Troops said they had found Sabaya's trademark sunglasses and backpack at the site of the June 7 clash in the dense jungle on the main southern island of Mindanao. 

Freed captives have said Sabaya led the pre-dawn raid on an upscale resort on May 27, 2001, in which the guerrillas snatched 20 hostages including Burnham and his wife Gracia, of Wichita, Kan., and Guillermo Sobero of Corona, Calif. 

Using speedboats purchased with ransoms from a mass abduction a year earlier, the guerrillas ferried the hostages across the Sulu Sea to Basilan island, where the military launched a massive search. 

The United States sent 1,000 American troops to provide training and high-tech support to undertrained and ill-equipped Philippine troops. 

Abu Sayyaf — "Bearer of the Sword" in Arabic — is the guerrilla name of founder Abdurajak Abubakar Janjalani, said to be a former member of a larger Muslim rebel group, the Moro National Liberation Front. He studied Islam in Libya, Syria and Saudi Arabia and fought in Afghanistan. He was killed in a clash with police in late 1998. 

The group reportedly got early support from the Al Qaeda terrorist network, but had become more of a bandit gang, thriving on kidnapping-for-ransom and killing captives whose families couldn't afford to pay. 

Sabaya, whose real name is Aldam Tilao, once studied computer engineering. After visiting Saudi Arabia for work, he returned home in the late 1980s and joined the Abu Sayyaf. 

Sabaya, expressing anger over the government's refusal to bring in outside hostage negotiators, threatened last June to kill Sobero. Days later, claiming a government double-cross, he called a local radio station to say he had beheaded the American. 

Months later, Sobero's remains were found scattered in the jungle. 

Using hostages as human shields, the Abu Sayyaf snatched a total of 102 people over several months. Some were killed; others escaped and the rest were freed, reportedly for large ransoms. Only the Burnhams and Yap were left when troops found footprints in the jungle on June 7 and tracked down the rebels. 

Martin Burnham and Yap were killed in the ensuing battle, and Gracia was shot through the thigh.