BACOLOD, Philippines (AP) — Gunmen killed nine members of a farmers' group who occupied part of a privately owned sugarcane plantation in an apparent land conflict in the central Philippines, police said Sunday.

The victims were resting in a tent Saturday night when about 10 gunmen opened fire, police said. At least four farmers survived the attack at the plantation field in Sagay city in Negros Occidental province, which has a history of bloody land feuds.

"There are groups fighting over that land," Sagay police Chief Inspector Roberto Mansueto said.

At least two of the victims may have fired back at the attackers because spent pistol and shotgun casings were found in the area, Mansueto said.

"Witnesses say they heard only a few initial shots. Apparently the victims were just being threatened," Mansueto told reporters. "But later there seemed to have been an exchange of fire."

The National Federation of Sugar Workers condemned the killings of its members, who included four women and two minors. The group said the victims were forced to plant vegetables and root crops to feed their families on idle land that's covered by the government's land reform program but remained undistributed to poor farmers.

Two other peasant leaders belonging to the federation were killed in Sagay city last December and in February this year by suspected pro-government forces, the group said. It said that about 45 farmers asserting their land rights have been killed on Negros island under President Rodrigo Duterte's administration.

Instead of offering an effective land reform program, Duterte's government "red baits those who assert their rights to the land," the group said, referring to pronouncements by civilian and military officials linking protesting farmers to communist guerrillas to justify attacks on activists.

Duterte's office condemned the killings, saying it "adheres to the principle that the right to life shall remain unthreatened by proprietary interests, and this extends to agrarian settings."

"Families of the victims of this extremely cruel act can count on the government that it will enforce the full wrath of the law against its perpetrators," presidential spokesman Salvador Panelo said in a statement.

In September 1985, government forces opened fire on protesters, many of them farmers, in Negros Occidental province as they were commemorating the 1972 declaration of martial law by then-President Ferdinand Marcos. Several died in an event that left-wing activists still mark each year.

Landlessness and crushing poverty, especially in rural regions, have been blamed for fueling a communist insurgency that has raged for nearly half a century in one of Asia's longest rebellions.

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