THE HAGUE, Netherlands — The International Criminal Court unsealed Monday an arrest warrant for a prominent Philippine senator linked to the deadly “war on drugs” overseen by ex-President Rodrigo Duterte, which allegedly involved the extrajudicial killings of suspects.

The warrant, originally issued confidentially in November, charges Ronald Marapon dela Rosa, a former Philippine national police chief and a Duterte ally, with the crime against humanity of murder of “no less than 32 persons” allegedly committed between July 2016 and the end of April 2018.

Duterte, dela Rosa and other police officials have denied authorizing the killings of drug suspects, who, they said, were shot dead after allegedly threatening law enforcers. Duterte openly and repeatedly threatened drug suspects with death while in office.

The warrant said judges decided after studying evidence submitted by prosecutors that dela Rosa “made essential contributions to committing the alleged crime” of murder and listed him as an “indirect co-perpetrator.”

Dela Rosa appeared unexpectedly in the Philippines Senate on Monday after being summoned as part of a new investigation into the alleged extrajudicial killings. National Bureau of Investigation officers tried to run after dela Rosa as he entered the Senate, but failed to reach him as he dashed into the plenary hall and sought the protection of fellow senators.

Former Philippines Senator Antonio Trillanes showed the warrant to the media in Manila on Monday, and the ICC confirmed its authenticity.

Dela Rosa once served as the national police chief under Duterte, and was the first to enforce the bloody campaign against illegal drugs that left thousands of mostly petty suspects dead. Philippine police officials have summoned dela Rosa to appear before them for an investigation into his role in the Duterte-era killings.

Maria Elena Vignoli, senior international justice counsel at Human Rights Watch, welcomed the warrant, calling it “another blow to the wall of impunity protecting those who allegedly committed atrocities during the Philippines’ murderous ‘drug war.’”

She called on Philippine authorities to swiftly detain dela Rosa and send him to the court in The Hague.

Duterte was arrested in March last year and detained in the Netherlands on charges of crimes against humanity. The charges are also linked to deadly anti-drugs crackdowns he ordered while he was in office. He denies the charges, but judges have ruled that there is enough evidence to warrant his standing trial. No date has been set for the case to start and Duterte has skipped several court hearings due to ill health.

The thousands of killings of mostly impoverished drug suspects took place when Duterte was mayor of the southern city of Davao and after he became president in 2016. The killings during police raids alarmed human rights groups and Western governments, led by the United States.