Former drug dependents undergoing rehabilitation make coffins as part of a local government drug rehabilitation program for people involved with drugs "Shabu" (Meth) in Olongapo city in northern Philippines, October 5, 2016. Erik De Castro, Reuters

OLONGAPO, Philippines - Some drug users seeking to avoid becoming a bloody statistic in Philippines President Rodrigo Duterte's crackdown on narcotics, are going into a rehabilitation program that teaches them how to make coffins.

More than 700,000 drug users and pushers have registered with the authorities in a process termed "surrendering", but there are few programs or facilities to help most of them.

But in Olongapo, a city of 220,000 three hours north of Manila, drug users are taught carpentry skills and paid 5,000 Philippine pesos ($103) a month to build wooden coffins as part of the local government's livelihood and rehabilitation program.

"I knew that if I don't change, I will be in one of those caskets," said a 44-year-old man, who declined to be named, pointing to coffins in a small workshop where nine other former drug users were also working.

Since Duterte was sworn into office on June 30, more than 3,600 people have been killed, mostly alleged drug users and dealers, in police operations and suspected vigilante killings.

At least 400 self-confessed drug users have surrendered to Olongapo police since June and will be included in the coffin building program in the coming months.

The caskets, made of simple plywood and painted white, are provided to the poorest families in the city who are unable to afford funeral services, government officials said.

Filipinos gave Duterte an "excellent" rating for his war on drugs, an opinion poll showed on Friday, but there was an indication of possible unease over the deadly campaign as most respondents said it was important to arrest suspects alive.

Western governments and human rights groups have expressed concern and called for thorough investigations into the killings.