Manila: Outspoken Philippine President Rodrigo Duterte said on Monday that the families of people killed in his controversial war on drugs will not receive "justice", rejecting calls from rights groups seeking redress for the thousands of deaths.

More than 4,200 suspected drug dealers have been killed by police in Duterte's anti-narcotics campaign since June 2016, as well as several thousand more by unknown gunmen who authorities have described as vigilantes, or rival gang members.

Rights groups and critics of the campaign say some of the killings were summary executions.

Police deny the allegations, saying they had to use deadly force because the suspects were armed and had resisted arrest. They also deny activist allegations that they have falsified reports, staged crime scenes and systematically murdered small-time peddlers and users.

"If you think that you can get justice simply because you lost somebody who's a <expletive> into drugs, I'm sorry to tell you I will not allow it," Duterte said in a speech on Monday.

He also reiterated that he would not allow the police and the military to go to jail for killing drug users and pushers.

"If you are shot and I know you are a drug lord, I will run over you five times," said Duterte, who won the presidency in May 2016 on a platform of fighting corruption, crime and drugs.

Duterte has stopped police anti-drugs operations twice due to questions over the conduct of the force, including the killing of a teenager in a supposed anti-drug operation in 2017.

The 73-year old leader's popularity had not diminished, according to opinion polls, despite drawing international criticism for his bloody war on drugs and human rights record.