President Rodrigo Duterte said on Friday that his son, former Davao City Vice Mayor Paolo "Pulong" Duterte, will run for Congress in next year's midterm elections to get back at opposition Senator Antonio Trillanes IV.

In a speech before the Filipino community in Papua New Guinea, Duterte said that his son and Trillanes could even have a gun duel at the House of Representatives.

"Pulong will surely get back (at Trillanes). He will be running for Congress...in Congress, you can shoot each other," he said, adding that in case Paolo is killed, he would just have him buried.

Duterte said his son would want to seek revenge with Trillanes after he was summoned at the Senate and Trillanes grilled him over the his alleged involvement in illegal drugs. The younger Duterte denied the allegation.

But Paolo and Trillanes' face-off in Congress might not happen as the senator earlier said that he would not run for any elective post in the 2019 polls.

Trillanes is on his second and last term as senator. He could run for other post next year, but he did not file any certificate of candidacy.

In the same speech, Duterte likened Magadalo, a group of former mutineers, including Trillanes, to ISIS.

"Be careful with Magdalo. These are the rebel soldiers there in Makati...the fools are like ISIS," he said.

The Magdalo group was behind the at least two failed coups d'etat against the administration of then President Gloria Macapagal-Arroyo.

Trillanes and the other Magdalo members were given amnesty by former President Beigno Aquino III.

But Duterte earlier issued a proclamation declaring as void ab initio Aquino's amnesty to Trillanes, the President's staunchest critic.

Trillanes has been questioning the the legality of the proclation and the warrant of arrest against him before the courts. Celerina Monte/DMS