MANILA - Opposition bet and human rights lawyer Chel Diokno on Thursday said the government's anti-narcotics campaign is a deliberate attack on the poor.

Diokno made the statement in a video conference call with DRCNet Foundation, a United Nations-accredited anti-drug network.

The senatorial candidate was asked regarding the basis of complaints against President Rodrigo Duterte before the International Criminal Court (ICC) for crimes allegedly committed under his administration's war on drugs.

"Our position is that the killings in the name of the war on drugs constitute as crimes against humanity. Not just because of the number of killings but because they are a deliberate attack on a very clear segment of the civilian population here in the country," he said.

"We have witnessed a very deliberate and clear-cut pattern of killings, especially of the poor people who are put into lists. These are lists that are...very arbitrary and subjective. But those lists have been weaponized and have become basis for the killings of thousands of Filipinos."

The Philippines officially withdrew from the ICC last Sunday, March 17, a year after Duterte unilaterally pulled out from the international body after it announced the beginning of its preliminary examination into the drug war.

Diokno said Duterte has not done anything to investigate the alleged extrajudicial killings.

"While the President clearly by now has a lot of knowledge of abuses committed by his men in uniform, he has not lifted any fingers to investigate them properly. And their apparatus for doing that is not utilized," he said.

Diokno also told the anti-drug network of the death threats being received by Catholic bishops who had openly criticized the drug war.

"The Philippines is predominantly Catholic in composition and the Catholic Church has come out publicly contesting the killings. In fact, some of the Catholic bishops have been subjected to death threats, probably related to the work they’re doing in the communities, helping the victims of extrajudicial killings," he said,

"The Church as an institution has come out to condemn the killings and that has [taken] them at odds with the government."

• Duterte critic Bishop David admits getting death threats

The conference call was a side event at 62nd session of the UN Commission on Narcotic Drugs.

Foreign Affairs Secretary Teodoro Locsin Jr. earlier touted the Duterte administration's anti-narcotics campaign before the commission, saying some 1.4 million Filipino drug users have surrendered "for rehabilitation" to authorities under the drug war.

• Locsin: 1.4 million Pinoys surrendered for rehab under drug war

Some 5,000 drug suspects have been killed since Duterte assumed presidency in 2016, but human rights groups say this figure is severely understated.

The campaign has drawn widespread criticism for alleged state-sponsored killings, which the government has denied.