The group, which murdered two Canadians last year, demanded a ransom for his release.
Young children could face adult charges and even the death penalty.
Catholic parishes around the country had denounced the extrajudicial killings as a 'reign of terror.'
Sermons in churches throughout the country target the extrajudicial killings as part of the war on drugs.
The Philippines' leader said he would target more "son of a bitch" traffickers and drug dealers.
Duterte might have called off the cops, but the killings of drug users and pushers continue.
The rights group claims Duterte's drugs war involves extrajudicial executions and falsified evidence.
More than 7,000 people have been killed since Duterte initiated the crackdown last summer.
Philippines president threatens to rip up a security treaty.
Philippines president says he would impose restrictions if the drug problem deteriorates 'into something really very virulent.'
The International Maritime Bureau said the waters off the southern Philippines have become increasingly dangerous.
One guard was killed, while eight prisoners have been caught—two surrendered and six were killed.
The president's threat to impose a firecracker ban achieved a "remarkable" decline in accidents.
The fiery-tempered former prosecutor said he once hurled a Chinese man suspected of rape and murder out of a helicopter.
A survey showed that a majority of Filipinos saw the drugs war as excellent, but disapproved of killing criminals.
Despite its rival claim to the Spratly Islands, Manila will not issue any diplomatic protest to China.
President Rodrigo Duterte has told police they may "shoot to kill" drug dealers.