The Philippine government said on Friday it intended to appeal an International Criminal Court decision to reopen an inquiry into Manila's brutal anti-drug campaign, which left thousands dead.

The Hague-based tribunal launched the enquiry in 2019 but suspended it later that year at the request of the government of then Philippine president Rodrigo Duterte, who had launched the crackdown in 2016, with Manila saying it would re-examine cases of alleged abuses.

Announcing the probe's resumption on Thursday, the ICC said its pre-trial chamber was "not satisfied that the Philippines is undertaking relevant investigations that would warrant a deferral of the court's investigations".

Menardo Guevarra, the chief lawyer of President Ferdinand Marcos' government, said: "It is our intention to exhaust our legal remedies, more particularly elevating the matter to the ICC appeals chamber."

Officially, 6,181 people were killed in Duterte's "war on drugs" but rights groups say that up to 30,000 may have been killed, some innocent victims, and that corruption was rife among security forces that acted with impunity.

President Marcos, elected in a landslide last year, has vowed to continue the drug war but with a focus on prevention and rehabilitation. He has, so far, ruled out reversing Duterte's decision to pull the Philippines out of the ICC.

"We wish to emphasise that our own domestic investigative and judicial processes should take precedence" over the ICC, said Guevarra.

"We can show that despite structural and resource limitations in our legal system, it is still a well-functioning system that yields positive results in its own time," he added. (AFP)