MANILA - President Rodrigo Duterte on Friday lashed out at the communist New People's Army (NPA), saying provinces are unable to develop because of the rebels' presence.

"Sabi ko, look, the reason why we cannot develop fully is the countryside are --- the countryside is infested with parasites like you. You do not work, you exact taxation," Duterte said during an event for agrarian reform beneficiaries in Davao City.

Duterte said some development projects in provinces are blocked by communist rebels' presence. He compared the NPA ideology to that of the Islamic State terror group.

"With the communist theories and your ideologies which is rotten already --- it is a corrupt just like the ISIS, you fight, you kill," he said.

Duterte denounced NPA rebels for their alleged involvement in the torture and killing of four cops in Ayungon town, Negros Oriental.

"You know what you did in Negros, it did --- is not just fighting. The danger there is you are now implementing the commune system of the discredited communist party strategy," Duterte said.

"I’d like to say to the communists, you have crossed the red line," he said.

The slain policemen were found tied with gunshots and bruises all over their bodies in a field in Ayungon last July 2018.

• 4 pulis patay sa pananambang sa Negros Oriental

Duterte, who served as mayor of Davao City for 22 years, claimed he never allowed the military or the police to torture captured NPA members in his city.

"You know, I have been mayor of this city for 23 years. There never was a time that the military or myself allowed torture or to hurt people who surrendered from the NPAs or captured. Wala talaga. I will never allow it," the chief executive said.

"In the 23 years, we never did that. The communist here who take hostage of our soldiers. I go to the mountains every now and then with Bong, bring a helicopter, and if there are many I bring two, three and retrieve them from the custody. And they have always been honoring that no --- no torture or no inhuman," he said.

But the rebels, Duterte said, did not show the same courtesy. The President said he would not let the NPA get away with it.

"I served notice the other day that I will not take it sitting down. I will just maybe… I told my military," he said.

Duterte said severe measures will be enforced although he did not elaborate. - With a report from Joyce Balancio, ABS-CBN News