Manila  - Three Muslim separatist rebels and a government militiaman were killed in a clash in a southern Philippine province, an army spokesman said Friday.

Lieutenant Colonel Jonathan Ponce said the firefight erupted when Moro Islamic Liberation Front (MILF) guerrillas opened fire at patrolling militiamen in Kalamansig town in Sultan Kudarat province, 930 kilometres south of Manila, on Thursday.

The 30-minute firefight resulted in the death of three MILF rebels and a militiaman, Ponce said.

In nearby Maguindanao province, soldiers recovered a cache of explosives, including 10 rounds of 81-millimetre mortar shells, in a hut in Upi town, also on Thursday.

Ponce said the explosives were suspected to belong to MILF rebels, who convert mortar shells into homemade bombs.

"It may be intended for bombing attacks," he said.

Last week, three bomb attacks rocked the cities of Cotabato and Kidapawan, injuring nine people.

Authorities said the bombings were likely perpetrated by extortion gangs, but they did not rule out the possibility that MILF rebels could be involved.

The MILF has been fighting for the establishment of a separate Islamic state in the southern region of Mindanao since 1978.

Peace talks between the MILF and the Philippine government have been suspended since August 2008 when the guerrillas launched a series of attacks in Mindanao, triggering fierce fighting with the military.

Nearly 300 people were killed in the attack and subsequent fighting, while more than 500,000 civilians were displaced by the violence.

The hostilities erupted after the Supreme Court stopped the signing of a territorial agreement between the MILF and the government that would have expanded a Muslim autonomous region in Mindanao.

The government hopes to resume peace talks with the MILF soon, but the rebel group has expressed hesitation to return to the negotiating table after the scrapping of the territorial agreement. (dpa)