The International Criminal Court on Wednesday authorized an investigation into the Philippine government's drug war that has led to thousands of killings by security forces that, judges say, may amount to crimes against humanity.

Thursday, Philippine President Rodrigo Duterte does not recognize teh court since the Philippines' withdrawal in 2019 from the Treaty of Rome, the founding text of the International Criminal Court.

He warned that "the government will prevent entry" into its territory for any member of this court in order to "collect information and evidence."

The Philippine president has stated on several occasions that the International Criminal Court has no authority and that he will not cooperate with what he called an "illegal" investigation. He even threatened to arrest the outgoing International Criminal Court prosecutor, Fatou Bensouda.

The court, set up in 2002 to try the world's worst atrocities, concluded there was a "reasonable basis" for talking about crimes against humanity and gave the green light Wednesday to open an investigation even though Manila withdrew from the court in 2019, after opening a preliminary investigation into the violence.

Bensouda announced in June that she had called for an investigation into the thousands of murders committed in the Philippines as part of the government's declared war on drugs.

The International Criminal Court has clarified that the so-called 'war on drugs' campaign cannot be considered a legitimate operation to maintain security, nor can killings be considered lawful, nor can they be considered as mere transgressions in the context of a legitimate operation.

Available documents indicate that “a generalized and systematic attack on civilians was launched in the implementation of or in pursuit of a state policy,” the international judges said in a statement.

The investigation will cover the period from 2011 to 2019.

- 12,000 to 30,000 dead -

Philippine President Rodrigo Duterte was elected in 2016 after a massive security crackdown promising to stamp out the drug trade by killing tens of thousands of delinquents.

The latest official figures show at least 6,181 people have been killed and more than 200,000 anti-drug operations carried out in the Asian archipelago, but human rights advocates estimate the actual death toll to be much higher.

ICC prosecutors estimate in court documents that between 12,000 and 30,000 people were killed.

They stated that Manila did not deny the killing of people during police operations, but it "constantly emphasized that these deaths were caused by security elements acting in self-defense."

Although the Philippines withdrew from the ICC in 2019, the court still has the power to consider crimes that may have been committed on its territory when it was a member state of the Rome Treaty.

- Police and militiamen commit killings -

According to prosecutors, unlawful killings were also committed by local police officers and militia elements before 2016 in the Davao region (southern Philippines) where Duterte served as mayor.

It was perpetrated by a group calling itself the Davao Death Squad.

Prosecutors said the majority of the victims were young men suspected of small-scale drug dealing or petty crimes such as theft and drug use, but that "gang members and street children were also killed."

Human rights organizations praised the court's decision, stressing the "need to control" Duterte's "deadly war on drugs."

"Families of victims and survivors have reason to hope that those responsible for crimes against humanity can finally be brought to justice," said Carlos Conde, a researcher at Human Rights Watch.