At least four men were killed and 11 others wounded when a grenade exploded on Thursday at a bakery in the southern Philippines, a military spokesman said, blaming Maoist-led rebels for the attack.

Hours later, another group of communist New People's Army (NPA) guerrillas raided a town hall in a nearby province on the troubled southern island of Mindanao, wounding a police officer, and carted away three assault rifles and a handgun.

Major Armand Rico said two men and a woman on a motorcycle lobbed a grenade into the bakery in Nabunturan town at dawn on Thursday, killing three people on the spot.

"A dozen people were rushed to a nearby hospital, but one died while being treated," Rico said, adding NPA rebels were behind the attack.

"We believed the grenade attack was a punitive action for the failure of the business establishment to pay revolutionary taxes to the rebels."

Rico said several traders in Nabunturan, a mining town on Mindanao, have been getting extortion letters from the NPA, threatening to blow up their businesses if they ignored the demand.

In nearby Banay-banay town in Davao Oriental province, about 50 rebels on board two dump trucks raided the town hall, engaging a handful of police officers on duty in a fight.

"The rebels came pretending to apply for a rally permit, but disarmed some of the police officers guarding the town hall," Rico told reporters, adding soldiers were rushed to the area to reinforce some officers who put up a fight.

Rico said one police officer was wounded during a 30-minute firefight. The rebels took control of the town hall for a few minutes before fleeing with the guns and office equipment.

Last week, the rebels raided two town halls in Surigao del Norte province, stealing weapons and communications equipment, but soldiers caught up with the guerrillas, killing 15 of them and capturing a dozen others.

The Philippines has been battling communist rebels in 69 of 81 provinces across the country in a protracted conflict that has killed 40,000 people and stunted economic growth in one of Southeast Asia's poorest states.