The Philippines will from today no longer be part of the treaty that created the International Criminal Court (ICC).

The country's withdrawal from the Rome Statute comes a year after President Rodrigo Duterte complained about what he saw as a "concerted effort" by United Nations officials to paint him as "a ruthless and heartless violator of human rights".

He railed against the "baseless, unprecedented and outrageous attacks on my person".

Adopted and signed by 123 states in 1998 during a diplomatic conference in the Italian capital, the Rome Statute created the ICC and gave it jurisdiction over genocide, crimes against humanity and war crimes.

The ICC in February last year began a preliminary investigation into Mr Duterte's controversial crackdown on the narcotics trade.

The police say more than 5,000 suspects have been killed in shoot-outs during drug raids since Mr Duterte took office in mid-June, 2006.

But human rights activists insist the number has already surpassed 20,000 in the brutal drug war that has mostly targeted the country's poorest districts.

Two-thirds of those dead are believed to have been killed by paid assassins backed by the police.

Mr Duterte has been accused of "crimes against humanity" before the ICC for these extrajudicial killings.

The Philippines signed the Rome Statute in 2000, and ratified and endorsed it in 2011.

Rights advocates have filed a petition with the Supreme Court challenging Mr Duterte's decision to withdraw from the ICC, saying that it could derail efforts to investigate the killings and spur even more rights abuses.

The court, however, did not act on the petition. It is not known where the petition stands now that the withdrawal has become official.

The Philippines' withdrawal does not prevent the ICC from pursuing cases lodged against Mr Duterte.

But his spokesman Salvador Panelo said the government would not cooperate with any investigation. "They cannot do anything against us," he said.

Burundi was the first nation to leave the ICC, in 2017, amid investigations into "historic crimes against humanity" in the central African nation.