Manila, July 28 (IANS): Three soldiers were killed and 13 injured in an ambush by New People's Army (NPA) rebels in Kalinga province of the Philippines.

Brigade general Paul Atal, commander of the army's 503rd brigade, said the rebels first detonated landmines before opening fire on the troops who were aboard three military trucks and on the way back to their base, reported Xinhua news agency.

The incident occurred around 11:20 p.m. on Monday night in Apatan village in Pinukpuk town. The troops had been receiving reports about sightings of NPA rebels in Pinukpuk and in the nearby town of Balbalan, prompting the troops to launch operations against the rebels.

However, the operation was terminated, apparently after failing to engage the rebels.

"They were on the way back to their command post when they were ambushed," the official said.

He said the troops returned fire, resulting in a 25-minute skirmish.

"After the explosions, we fought back," said Atal, adding that NPA casualties remain unclear.

The armed forces declared Kalinga "insurgency free" in November 2010. The insurgency free branding was later renamed by the military as "peaceful and ready for further development."

The NPA has been waging a guerrilla campaign against the government in the countryside for four decades. The military estimates the NPA strength at more than 4,000 men.