Malacanang challenged on Thursday opposition Senator Antonio Trillanes IV to substantiate his allegation against presidential son Vice Mayor Paolo Duterte that he is a member of a drug triad.

In a press briefing, Presidential Spokesperson Ernesto Abella described Trillanes' accusation as "pretty drastic.

"Those are very serious allegations. He needs to have some pretty substantial evidence to support that statement," he said.

President Rodrigo Duterte's son, along with son-in-law, Manases Carpio, appeared before the Senate Blue Ribbon Committee investigating the P6.4 billion shabu shipment from China that was able to pass the Bureau of Customs' check last May.

During the hearing, Trillanes said he got information from "foreign intelligence" that Paolo was a member of the drug triad and his having a colored dragon-tattoo in his back was the proof of his membership.

He asked Paolo to show his back, which the latter refused as he invoked his right to privacy.

Asked if the president, who has no official schedule on Thursday in Davao City, watched the Senate hearing, Abella said he was not sure.

But Abella added, "I’m sure he is always on top of all events."

Duterte earlier said he advised Paolo and Carpio to attend the Senate probe, but they should invoke their constitutional right against self-incrimination, especially if Trillanes would be the one to ask question. Celerina Monte/DMS