President Rodrigo Duterte may declare martial law in Negros Oriental due to the spate of killings in the province during the past weeks.

In a press briefing on Thursday, Presidential Spokesperson Salvador Panelo said that during Duterte's speech at the anniversary of the National Intelligence Coordinating Agency Wednesday night, it appeared that Duterte would use his emergency powers "soon".

"The killings are alarming. We have a village, a barangay captain, a municipal mayor, four policemen and a lawyer (who were killed). The President doesn’t want this to happen. He wants it stopped, and the only way to do that is to use his emergency powers," he said.

He said the Constitution provides options for Duterte to address violence in Negros Oriental.

"He can call the Armed Force to quell lawless violence; he can declare martial law," said Panelo, also chief presidential legal counsel.

Asked if Duterte would approve if the security forces and local officials would recommend the declaration of martial in Negros Oriental, he said, "Certainly. He always follow the advice of those people in the know."

He said if Duterte will place the Visayan province under martial law, it could be a separate declaration with that in Mindanao.

The entire southern Philippines has been under martial law since May 23, 2017 following the attack in Marawi City by terrorists.

Panelo said Duterte is blaming the communist New People's Army for the violence in Negros Oriental.

"Because according to him (Duterte)...the unrest there has become widespread and it is being used by the communist rebels to use it as an excuse. And in fact he has even made the two provinces a quasi state, meaning to say that the land claimants there are involved in armed hostilities. And it is the communist rebels that arbitrarily choose who will occupy or own the land," Panelo said.

But he noted that the Reds were accusing the government of perpetrating the killings.

"According to them (NPA), we're the sponsor (of the killings) - that's part of their propaganda warfare - psychological," he said.

At least 21 people were reported killed in Negros Oriental since July 18, when four policemen were shot dead and allegedly tortured by the Maoist rebels. Celerina Monte/DMS