The communist New People's Army (NPA) was allegedly behind the massacre of nine sugar farmers in Negros Occidental, Malacanang said on Monday.

This as President Rodrigo Duterte is set to visit the wake of the slain farmers in Sagay town, according to former Special Assistant to the President Christopher "Bong" Go.

Presidential Spokesperson Salvador Panelo said the Palace condemns in the strongest possible terms the deaths of the workers.

"The Palace is deeply perturbed to learn about the incident and the Philippine National Police has already been ordered to conduct a thorough and impartial investigation on this dastardly act," he said in a statement.

He assured the families of the victims that they could count on the government that it will enforce the full wrath of the law against the perpetrators.

In separate radio interviews, Panelo, also chief presidential legal counsel, said based on the initial findings, the surviving victims allegedly identified those who attacked the farmers at Hacienda Nene were reportedly members of the Communist Party of the Philippines-New People's Army.

"Whatever the reasons may be, the investigation shows the CPP-NPA was behind the massacre," he said.

Panelo said there was also information the slain farmers were allegedly members of the legal front of the CPP-NPA.

"Those who were killed were allegedly new recruits," he said.

He said if the victims were new rebel recruits, "something is wrong with that. There could be a deeper (reason for that). Let's wait for a thorough investigation."

The slain farmers, reportedly members of the National Federation of Sugar Workers, were eating inside the tents when they were attacked by armed men on Saturday. Celerina Monte/DMS