By CARLOS H. CONDE

MANILA — Philippine authorities on Saturday said they had in custody a leader and founder of the Islamic extremist group involved in the bombing of a passenger ship here in 2004, which killed 116 people. It was the worst terrorist attack in Southeast Asia since the Bali bombings in October 2002, when 202 people died.

The suspect, Ruben Pestano Lavilla Jr., was deported Saturday from Bahrain, where he was arrested in July. The Philippine police said he had helped form the Rajah Solaiman Movement, which is among several rebel groups seeking a separate Islamic state for Filipino Muslims.

Officials said Mr. Lavilla’s arrest was a breakthrough in the Philippines’ antiterrorism efforts. The movement focuses on converting Christians to Islam and then training them to be terrorists. In addition to the 2004 bombing of the passenger ship, the Superferry 14, Mr. Lavilla is suspected of playing a role in a series of attacks in Makati City, the Philippine financial center, and in two other cities in the south on Feb. 14, 2005.

In June, the United States Treasury Department sought to tighten the financial pressure on the movement by designating the group and its members as “global terrorists.” The group is on the United Nations’ terrorist list as well. The Treasury said the movement had received money from sympathizers in Saudi Arabia and from at least one Filipino financier there, who channeled funds through Muslim charities in the Philippines.

The Treasury said it believed that Mr. Lavilla had taken over as the movement’s “political, religious and strategic leader” after the arrest in 2005 of its previous leader, Ahmed Santos.

Filipino and Western antiterrorism officials have linked his movement to the notoriously violent Abu Sayyaf rebel group and to Jemaah Islamiyah, the Southeast Asian terror network that Western and Asian intelligence agencies have tied to Al Qaeda.

Ricardo Blancaflor, a spokesman for the Philippine Anti-Terrorism Council, described Mr. Lavilla’s arrest and extradition as a “big boost” in Manila’s fight against terrorism. It remained unclear how Mr. Lavilla had managed to flee the Philippines, though officials speculated that “intelligence lapses” might have allowed him to slip away.

Officials also said Saturday that four Philippine marines had been killed and 10 wounded in an ambush, apparently by Abu Sayyaf militants, in Sulu Province in the southern Philippines.

In addition, the Moro Islamic Liberation Front, the main Islamic separatist group in the south, threatened on Sunday to abandon peace negotiations with the government because it had not yet signed a peace agreement that had been initialed by both sides.

Mohagher Iqbal, the front’s chief negotiator, told Reuters that his group would negotiate further only if Manila signed the agreement, which would cede sizable territory to Filipino Muslims.

“We’re not only disappointed and frustrated over the government’s decision to turn its back on the ancestral domain deal, we’ve completely lost trust and confidence in them,” Mr. Iqbal said on Sunday. “The fate of the peace negotiation rests solely in the hands of the government.”

The failure to sign the agreement has touched off renewed violence on the southern island of Mindanao. More than 300,000 people have been forced from their homes and 150 rebels have been killed, officials said.

Copyright 2008 The New York Times Company