MANILA: A Philippine farmer unearthed a mass grave with the skeletal remains of up to 30 people believed to be victims of an internal purge by communist rebels in the 1980s, the army said on Sunday.

Rommel Malinao was ploughing his field in a remote village in Quezon province, south of Manila, when he made the discovery on Saturday, army spokesman Major Harold Cabunoc said.

The army deployed a team to cordon off the site and with the help of police forensics experts exhumed the skeletons.

“As of last count, there were about 30 human skeletons,” Cabunoc told AFP.

“We believe these were victims of the New People's Army (NPA) 'kangaroo courts', which sentenced to death many members they had suspected as government intelligence agents.”

The NPA is the armed wing of the Communist Party of the Philippines, which has been waging a Maoist rebellion since 1969 - one of the longest-running communist insurgencies in Asia.

At its peak in the 1980s, NPA numbers were believed to have reached 26,000, but that is now down to only 4,000 fighters due to losses on the battle field.

The government alleges that in the mid-1980s, the NPA set up so-called 'kangaroo courts', which condemned to death hundreds believed to have become agents for the state.

Their bodies were believed to have been dumped in secret mass graves.

Various mass graves have been unearthed by the military since 2009, but Saturday's find was believed to contain the biggest number of skeletons so far, Cabunoc said.

Cabunoc added that villagers interviewed by the army near the site said many of their relatives whom they had suspected of joining the NPA went missing in the 1980s and had not been heard of since.

Some of the skeletons showed the hallmarks of torture, although further verification was needed, he said.

President Benigno Aquino re-opened peace talks with the communists in February last year but the negotiations have been delayed by the rebels' demand to release detained comrades.

It was not immediately clear how the discovery of the latest mass grave could affect the talks.