The Philippines is considering resuming membership of the International Criminal Court (ICC) nearly five years after it withdrew over objections to a bid by the court to investigate a bloody anti-narcotics campaign, the president said on Friday.

"There is also a question, should we return under the fold of the ICC, so that’s again under study. So we’ll just keep looking at it and see what our options are," President Ferdinand Marcos Jr told reporters.

The Philippines withdrew from the international tribunal in 2019 after then President Rodrigo Duterte questioned its authority to investigate the campaign against illegal drugs in which thousands of people were killed.

Marcos said questions over jurisdiction and sovereignty were still "problems" for the Philippines.

"Now if we can solve these problems, then that would be something else, but those questions are fundamental," Marcos said.

The ICC this year rejected a Philippine appeal to stop investigating Duterte's drug war. Marcos said in March he would cut off contact with the court after the decision.

In July, appeals judges at the ICC cleared the way for an investigation into the killings, a ruling that families of victims and right groups hailed as another step towards justice.

While Philippine officials still insist the international tribunal has no jurisdiction over it, some lawmakers have urged the government to rethink its position.

The country's lower congress began hearings this week urging the government to cooperate with the ICC prosecutor in its probe, after opposition lawmakers cited Duterte's admission in a television program that he used intelligence funds to fund extrajudicial killings when he was mayor of Davao City in the southern Philippines.

The move did not sit well with Vice-President Sara Duterte, the former president's daughter, who said on Thursday allowing an ICC probe is "patently unconstitutional"Harry Roque, the elder Duterte's former presidential spokesperson, said even if the Philippines returns to the ICC, the drug war cannot be investigated since "temporal jurisdiction was lost in 2019".

It "doesn't matter to (the) Dutertes. Jurisdiction will be prospective," Roque said in a text message.

Jean Encinas-Franco, a political science professor at the University of the Philippines, said Marcos' comments indicate he is "veering away" from the previous government's policies.

"It will be seen by a lot of people as breaking away from their alliance," she said.