Thousands of self-confessed drug pushers and users surrender to authorities in Tagum City on July 9, 2016. Bonna Pamplona, ABS-CBN News

TAGUM CITY - Thousands of self-confessed drug pushers and users turned themselves in to authorities on Saturday in the single biggest surrender so far under President Rodrigo Duterte, police said.

Duterte has vowed to wage a "bloody war" against illegal drugs and since his election win in May, over a hundred suspects have been killed, purportedly for attacking arresting officers.

He stepped up his unprecedented campaign this week by naming five police generals as protectors of drug syndicates. He also went on national television to detail an elaborate matrix of drug operations in the country.

Close to 4,000 suspects packed an auditorium in this city on Saturday, around 80 kilometers from Davao, where Duterte served as mayor for two decades, police said.

Thousands of self-confessed drug pushers and users sign a "commitment wall" in Tagum City on July 9, 2016. Bonna Pamplona, ABS-CBN News

The suspects, mostly men with baseball caps and dark shades worn on their heads, signed their names on a giant "commitment wall," and pledged to abandon drugs.

The suspects were not detained, but they will be "monitored" according to police.

Many other drug suspects have turned themselves in large numbers since Duterte assumed office on June 30 but Saturday's surrender was the biggest so far.

DEATH TOLL RISES

More drug suspects were gunned down on Saturday as legislators prepared to investigate the spate of killings, which have alarmed human rights groups.

Eight suspects were killed in Matalam town, North Cotabato province in an alleged shootout with police at around 2 a.m. Authorities claimed the group resisted arrest.

Bullets are recovered from the hideout of suspected drug dealers in North Cotabato on July 9, 2016. Arianne Apatan ABS-CBN News

In Bacolor, Pampanga north of Manila, the blindfolded and hogtied body of a man was found near a dike. A cardboard sign next to the body identified the man as a "rapist" and "drug dealer."

In Naga City, brothers and alleged drug ring leaders Alfie and Jose Alegre, the most wanted drug suspects in the area were arrested. Police recovered P300,000 worth of methamphetamine hydrochloride or "shabu" from the suspects.

Brothers and alleged drug ring leaders Alfie and Jose Alegre are arrested in Naga City on July 9, 2016. Jessa Mella, ABS-CBN News

As the deaths mounted, National Police Chief Ronald "Bato" dela Rosa told his men this week to mount only "legitimate" operations. He also said he was against vigilante killings.

Dela Rosa said roughly 120 drug suspects, including alleged Cebu kingpin Jeffrey “Jaguar” Diaz, have been killed by police in the last three months and there will be “more to come." -- reports from Bonna Pamplona, Arianne Apatan, and Jessa Mella, ABS-CBN News