MANILA- United Nations Special Rapporteur Agnes Callamard urged the Philippines to make sure that the death of 17-year-old Kian Delos Santos would be the last in the country's war on drugs.

Callamard in a tweet Saturday offered condolences to the Delos Santos family who buried the slain teen on the same day.

"My heart-felt condolences to #kian family and to all families victimized by this cruel war. #Makehisdeaththelast #Philippines," she said.

My heart-felt condolences to #kian family and to all families victimized by this cruel war. #Makehisdeaththelast #Philippines

— Agnes Callamard (@AgnesCallamard) August 26, 2017

She earlier branded as "murder" the death of the boy and called for a probe on "all unlawful deaths."

• Callamard on Kian's slay: This is murder

Delos Santos was killed in a controversial anti-drug operation last Aug. 16. Policemen alleged that the teen was a drug runner for his father and uncle, an accusation that his family has strongly denied.

The incident has drawn public condemnation as security footage and witness statements suggest that the teen was executed.

Autopsy results showed that the boy sustained fatal gunshot wounds to the head while he was already on the ground kneeling.

• PNP, PAO agree on autopsy: Kian already down when shot

Malacañang on Saturday urged the public to trust the justice system under President Rodrigo Duterte as charges have been filed against cops linked to the boy's slay.

The Palace added that the teen's killing was a "wake-up call" for reforms in the government and law enforcement agencies after the Philippine National Police drew heavy criticism over the incident.

Callamard had been critical of the deaths under the Duterte administration and had sought an invitation to visit the country to investigate drug-related killings.

• Farewell, Kian: Slain teen laid to rest as family cries for justice