MANILA (REUTERS) - Philippine President Rodrigo Duterte distanced himself from a list of top drug suspects his office made public last year after another mayor on that list was killed last week, a move which Human Rights Watch denounced as "cowardly".

Mr Duterte in a late night address on Monday (Dec 7) apologised to the family of Mr Caesar Perez, a town mayor who, according to the police, was shot twice in the head by unidentified gunmen on Thursday night inside the town hall.

"That list is not mine. It is a collation. All that came from intelligence reports of drug enforcement, police and military," Mr Duterte said.

"I'm sorry if your father was there. But really, most of those (on the list) are into drugs. Your father might be an exception."

Mr Perez is not the first mayor on that list who had been killed by unidentified gunmen. In October last year, a town mayor in Mindanao was being transported by police to a prosecutor's office in Cebu City, in the central Philippines, when gunmen ambushed him and his police escorts.

Mr Phil Roberston, deputy Asia director at Human Rights Watch, said Mr Duterte cannot now deny involvement in the violence perpetrated against those on his lists, which "he has used as a public, political prop for years to shore up his popularity".

"For him to disavow how these lists were used by law enforcers to violate the civil liberties and human rights of those listed is not only disingenuous - it is cowardly," Mr Robertson said in a statement.

Mr Duterte's office made public last year a list of "narco-politicians," ahead of the May 2019 mid-term polls.

A United Nations report in June said tens of thousands of people may have been killed in the drug war amid "near impunity"for police and incitement to violence by top officials. The government rejected that as baseless.