The United Nations Human Rights Commission has urged the Philippines to launch a murder investigation into President Rodrigo Duterte over his claims that he killed three people as mayor of Davao City. There are also calls to examine the "appalling epidemic of extra-judicial killings" committed during the anti-drug crackdown he has launched since becoming president in June 2016.

Duterte told a gathering of businessmen that as mayor of Davao City he "personally" killed criminals as he prowled the streets. He later admitted killing three men involved in a kidnapping case during a police gunfight in the late 1980s – although he further clarified that he was unsure whether the bullets from his M16 rifle killed the suspects. The photos in this gallery show Duterte handling machine guns in the 1980s and 1990s.

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Late 1980s: Mayor Rodrigo Duterte (L) inspects an assault rifle at a shooting range in Davao City in the southern Philippines with regional police chief Miguel Abaya and Metrodiscom chief Franco CalidaRenato Lumawag/Reuters
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Mid-1990s: Mayor Rodrigo Duterte poses with his Uzi sub-machine gun in the mountainous village of Carmen in the Baguio District of Davao City in the southern PhilippinesRenato Lumawag/Reuters
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Early 1990s: Mayor Rodrigo Duterte assists a policeman to direct street traffic in downtown Davao City in the southern PhilippinesRenato Lumawag/Reuters

The brash-talking president suggested that he used to roam around his sprawling city as mayor on a big motorcycle to look for criminals to kill so policemen would emulate him. "In Davao, I used to do it personally. Just to show to the guys that, if I can do it, why can't you?" Duterte said. "I go around in Davao with a motorcycle, with a big bike around, and I would just patrol the streets looking for trouble. I was really looking for an encounter to be able to kill."

Justice Secretary Vitaliano Aguirre II has defended Duterte, saying the president often exaggerates killings of criminals to send a chilling warning to lawbreakers.

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1997: Mayor Rodrigo Duterte inspects the assault rifle of Senior Inspector Ronald Dela Rosa at a crime scene in the village of Tamugan in Davao City in the southern Philippines. Looking on is Davao Police Chief Isidro LapenaRenato Lumawag/Reuters
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1987: Rodrigo Duterte poses for a picture in Davao City in the southern Philippines, following his appointment as vice mayorRenato Lumawag/Reuters
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March 1998: Soldiers listen as Davao City mayor Rodrigo Duterte gives a lecture on fighting the illegal drug trade during an anti-drug seminar in Davao City in southern PhilippinesRenato Lumawag/Reuters
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24 August 2016: Philippine President Rodrigo Duterte makes a fist bump gesture with soldiers during a visit at Capinpin military camp in Tanay, Rizal in the PhilippinesErik de Castro/Reuters
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1997: Davao Mayor Zafiro Respicio (4th L) and Vice Mayor Rodrigo Duterte (2nd R) talk to feuding Bagobo tribes to settle a Pangayaw - or tribal war - in the hinterlands of Davao city in the southern PhilippinesRenato Lumawag/Reuters
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8 February 2004: Women from the slums of Davao hold pictures of their dead or missing sons, who were involved in petty theft or the drug trade. The mothers blame Davao city mayor Rodrigo Duterte for what happened to their sons, whom they believe were summarily executedRomeo Ranoco/Reuters

Duterte has also revealed that he once threw a suspected kidnapper out of a moving helicopter when he was mayor of Davos City. After visiting areas affected by Typhoon Nina, Duterte gave a speech at the Camarines Sur provincial capital, during which he elaborated on his plans to crackdown on corruption within the government. "If you are corrupt I will fetch you with a helicopter and I will throw you out on the way to Manila," he said. "I have done that before, why should I not do it again?"

The president has brought the iron-fist approach he used to rule Davao to the capital Manila. Since taking office in June, Duterte has obsessively overseen the crackdown on illegal drugs that has left more than 6,000 people dead. About a third died in police anti-narcotics operations and the rest were killed by motorcycle-riding masked men and vigilante groups.

The former crime-busting mayor of the southern city of Davao had said that the war on drugs would be over within six months but has since pushed back the deadline. Last month he said that he will continue "until the last pusher drops dead".