Al-Qaeda-linked Abu Sayyaf group, on the US "terror list", has been suspected to be involved [File: AFP]

Philippine troops have defused a bomb outside a school in the country''s southern province a day after another blast destroyed a lodging house and a third explosive was found near a hotel.

Military forces safely defused the bomb, believed to be made from ammonium nitrate and attached to two cellular phones, after soldiers on patrol discovered the explosive in a biscuit can in front of the school compound in Lamitan town in the island province of Basilan, Colonel Alex Macario, the provincial military commander, said on Sunday.

Al-Qaeda-linked Abu Sayyaf group, which is on the US list of "terrorist" groups, has been suspected to be involved in the attacks.

The area was cordoned off as a soldier, taking cover behind a tree, cut the wires protruding from the explosive with a long bamboo pole fitted with metal hooks, according to witnesses.

Security was tightened in the area after yesterday''s explosion at the lodging house in the Christian town in a predominantly Muslim region.

The blast destroyed the small wood and concrete building but caused no injuries, Macario said.

Two men who checked in a hotel, often used by transient rubber plantation workers, left before the blast.

The owner apparently resisted an extortion attempt by an armed group before the attack, Felicisimo Khu, the regional police commander, said.

Shortly after the blast, troops found another bomb, which was packed with nails for greater impact, near a budget hotel in Basilan''s capital city of Isabela, officials said.

Abu Sayyaf ties

The army received intelligence that Abu Sayyaf fighters have planned to bomb a cathedral, small hotels and gas stations in Basilan, about 880 kilometres south of the capital Manila, Macario said.

The Abu Sayyaf is estimated to have 410 fighters in Basilan, where the group was founded in the early 1990s, and in nearby Zamboanga peninsula and the island provinces of Jolo and Tawi Tawi, according to a government threat assessment report.

The rebels have been grappling with the loss of several senior leaders and factionalism, but remain a key security threat to the country. They staged at least 11 kidnappings last year, enabling them to raise $704,000 in ransom, the report said.

Although it has been crippled by years of US-backed Philippine offensives, the Abu Sayyaf has endured and continued to be blamed for bombings, kidnappings for ransom, extortion and other acts of banditry in at least four impoverished southern provinces.

Source: Agencies