MANILA, Philippines - US soldiers were pulled out of a school project in Jolo, Sulu, and their movements limited to a camp following the explosion on Tuesday that killed two of them and a Filipino Marine.

The Armed Forces of the Philippines has also doubled the Americans? security and reinforced detachments and deployed additional quick-reaction forces in Jolo, AFP spokesperson Lt. Col. Romeo Brawner Jr. told reporters at Camp Aguinaldo Wednesday.

"In the meantime, we are limiting their movement but if they want to go out of the camp, the military provides them double security," Brawner said.

In a phone patch interview, Western Mindanao Command Maj. Gen. Ben Dolorfino said US authorities have already pulled out the Seabees, a construction battalion of the US Navy, involved in the school construction in Barangay Kagay.

"They are now in Camp Bautista but we will continue providing security to their projects," Dolorfino said. "They have been totally pulled out but they are determined to continue with the project but probably it might be continued by US engineers or they might subcontract it."

Brawner said that military operations in Sulu will not be affected even if there was such a pullout of US troops in the area.

Not disclosing any figure for security purposes, Dolorfino said that following the explosion caused by an improvised explosive device, the military has already called for augmentation of quick reactionary forces from Basilan.

"We can easily move them around Jolo even at nighttime," he pointed out.

While the general headquarters was cautious in pinpointing the perpetrators of the blast that killed two American soldiers as their vehicle passed in Barangay Kagay in Indanan town, Dolorfino said there was strong indication that the Abu Sayyaf bandit group was behind it.

A handful of American soldiers escorted by Filipino Marines had just inspected a school project in Sitio Laum Saing and were heading back to a Marine detachment in a US Hummer when the blast occurred Tuesday morning.

"There have been many incidents already and there is a very strong indication that the Abu Sayyaf wants to retaliate,? said Dolorfino.

Before Tuesday's explosion, a grenade was lobbed at US troops unloading supplies at the Jolo pier, which prompted the American soldiers to fire their weapons. A few hours after the blast, suspected Abu Sayyaf bandits bombed a police outpost in Patikul, Sulu.

The manner by which the Abu Sayyaf was mounting its attacks clearly suggested that the bandit group was already running low on manpower and ammunition, said the ground commander.

"Maybe they are still waiting for their supply of ammunition from wherever they get it so they resort to explosives and to asymmetric warfare without using people to continue retaliating against us," he said.

Brawner said the investigators have yet to fully establish the identities of those behind Tuesday's attack.

When asked if the Abu Sayyaf was behind it, he replied, "It is possible,? pointing out that the component of the bomb was that of an improvised explosive device.

"But we are careful not to point at any group for now," said Brawner.