MANILA (Reuters) -- Philippine communist rebels said on Wednesday they seized 29 assault rifles and bullets in a raid on an army outpost on the troubled southern island of Mindanao.

The military declined to comment, saying it was still trying to verify the incident.

The New People's Army (NPA), fighting one of the world's oldest communist insurgencies, often attacks remote military and police facilities to steal weapons and ammunition.

"Our fighters caught them by complete surprise," Cesar Renerio, a rebel spokesman in Bukidnon province, told reporters, saying dozens of NPA guerrillas raided an army base outside Valencia City on Tuesday night.

"Several members of a paramilitary unit inside the base did not offer any resistance. At least 29 M-16 rifles were taken from the detachment."

The Philippines, Washington's closest security partner in Southeast Asia, estimates NPA membership at around 7,000 down from a peak of more than 25,000 in the mid-1980s.

Fuelled by widespread poverty and a sense of injustice, especially in rural areas, the NPA has been waging a violent, hit-and-run insurgency since the late 1960s and is active in 69 of 79 provinces.

At least 40,000 people have been killed in the conflict.

Peace talks with the communists, brokered by Norway, stalled in 2004 when Manila refused to persuade the United States and some European states to remove the NPA from terror blacklists.