MANILA—President Rodrigo Duterte on Sunday called Senator Antonio Trillanes "political ISIS" for constantly attacking him.

Duterte made the remark past midnight when he took questions from the media after attending the birthday celebration of Congressman Karlo Nograles in Davao City Saturday night.

"Si Trillanes iyong political ISIS. Walang alam, basta gusto lang bira nang bira. Akala niya tama siya. Ang nakakatawa dyan, when he talks, it’s as if talagang alam niya ang batas," the president said.

Trillanes has called for Duterte's son, Davao City Vice-Mayor Paolo Duterte, and son-in-law Manse Carpio to appear in Senate hearings and answer allegations that they accepted millions of pesos in grease money.

• READ: Duterte defends son-in-law anew, calls Trillanes corruption allegations trash

The president said he has advised his son to attend the Senate inquiry.

"Ako, ang advice ko kay Pulong, punta ka doon, then pagdating mo doon sabihin mo, 'I will not answer you, I’m invoking my right of silence kasi noong eleksiyon pa, hindi pa president ang tatay ko binibira mo na kami,' " he said.

"So if you want evidence, Mr. Trililing, do not get it from the mouth of other people, go somewhere else. Kung iyong tinitira gusto mo ring ipitin, hindi ka abugado hindi ka marunong niyan. Ang sagot sa’yo, 'I refuse to answer your question because you intend to incriminate me.' You have already assumed I am guilty so what's the point of answering it?"

Malacañang on Saturday said it might not be necessary to summon the younger Duterte and Carpio to the Senate after they were cleared by Customs broker Mark Taguba of any involvement.

Taguba previously mentioned a "Tita Nani" who he supposedly met through a "Davao group" when lawmakers asked him to name personalities involved in bribery activities at the Bureau of Customs (BOC).

• READ: Witness says he gave bribes to 11 Customs officials per week

This group, Taguba said, is allegedly backed by a "vice mayor." However, he said, those involved could have just resorted to namedropping an official to seal a deal.