Five soldiers were killed and six others were injured in an ambush staged by suspected New People's Army (NPA) rebels in north Philippine province of Ilocos Sur on Thursday night, said military officials on Friday.

Mark Anthony Ruelos, public affairs officer of the Army's 7th Infantry Division, said soldiers were returning from a law enforcement operation with policemen when they were ambushed by 30 suspected NPA rebels around 7 p.m. local time at Legleg village in Quirino town.

Ruelos said they were verifying whether the NPA was specifically involved in this incident as there are other private armed groups operating in that area.

The military said the firefight lasted for 15 to 20 minutes before suspects withdrew. Troops from the 81st Infantry Battalion have been ordered to conduct pursuit operations for the suspects.

The NPA has been waging a guerrilla campaign against the government in the countryside for four decades. Military estimates the NPA strength at more than 4,000 men scattered in over 60 guerrilla fronts throughout the country.