COTABATO, PHILIPPINES - Five people were killed and at least 34 wounded in a suspected Muslim rebel bomb attack outside a Catholic  church in the strife-torn southern Philippines Sunday, officials said.

A lone suspect left a home-made device outside the Immaculate Conception cathedral in Cotabato city which exploded just as the congregation was leaving early morning mass, officials said.

The church was not heavily damaged as a restaurant across the street appeared to have absorbed much of the impact, witnesses said. Ordnance experts searched for clues among blood-spattered debris on the road outside the church.

Police said four people, including two soldiers, were killed at the scene, while another died of his injuries in hospital. Many of the wounded were women and children, according to Froi Cordero, a priest who helped bring the casualties to hospital.

President Gloria Arroyo directed security forces 'to get to the bottom of the blast, arrest those responsible as soon as possible' and ensure security in the city of about 200,000, her spokesman Cerge Remonde said.

Arroyo's chief adviser for the south, Jesus Dureza, described the bombing as 'an act of terrorism' and a 'murderous act of insanity'.

'I condemn this incident that attacked innocent civilians,' Sema said.

City police chief Superintendent Willie Dangane said no one had claimed responsibility for the attack but confirmed that the suspected bomber was arrested as he tried to bring another device into the church.

Regional military spokesman Lieutenant Colonel Jonathan Ponce was quick to blame the separatist Moro Islamic Liberation Front (MILF) for the blast.

'The special operations group of the MILF is behind this,' Ponce said, adding that the MILF had carried out similar attacks in recent weeks.

He said a bomb also allegedly planted by MILF rebels exploded in the nearby town of Datu Piang late Saturday, wounding three people.

'They are getting desperate because of the military operations,' Ponce said, stressing that the attacks were apparently meant to divert military attention. The military said it had received intelligence reports earlier indicating that the MILF was to carry out bomb attacks in major cities in Mindanao, the main southern island where they have been fighting for an independent Islamic state over the past three decades.

'That was why we had stepped up our troop visibility. But we only have so much troops and we can't cover all' of Mindanao, said army spokesman Lieutenant Colonel Romeo Brawner. MILF spokesman Eid Kabalu however denied the accusation, saying attacking civilians was against Islamic principles.

'The army has already blamed us even as an investigation into the bombing is yet to be carried out,' Kabalu said by telephone from the south. He said the bombing could also be the work of right-wing saboteurs opposed to any possible resumption of peace talks.

The 12,000-strong MILF broke a five-year-old ceasefire in August 2008, launching deadly attacks across several towns and provinces in Mindanao after a court rejected a proposed deal with the government that would have given them control over vast lands they considered as their 'ancestral domain'.

The fighting that followed left nearly 300 civilians and combatants dead, while more than half a million were displaced. Many have returned to their homes even as sporadic clashes have persisted. But the government says more than 300,000 evacuees still live in various camps in Mindanao.