JOHN PAUL LOPEZ, a man accused of helping a Philippine gunman kill seven people and wound 12 others has been detained as police investigate the motive for the drug-fuelled rampage, officials said on Saturday.

Witnesses told police that the arrested suspect helped reload a semi-automatic pistol as the gunman, later shot dead by police, went house to house in search of people to attack at a slum neighborhood in Kawit, Cavite.

Police arrested John Paul in Imus town in Kawit on Friday, hours after gunman Rolando Bae was killed in a firefight with police, said Chief Supt. Generoso Cerbo, National Police spokesman.

"We are investigating the level of his involvement, but definitely he faces criminal charges," Cerbo said of the alleged accomplice.

Lopez said that Bae forced him at gunpoint to load the clip of the .45-caliber pistol between the shootings, Cerbo told Agence France-Presse.

"If that is proven false, he would be charged with many murders," Cerbo added.

Gov. Juanito Victor Remulla of Cavite said that relatives led police to Lopez.

Remulla also said in an interview on a local radio that the authorities doubted the suspect's version of events.

"He changed the clip three or four times as Bae broke into houses. He [Lopez] could have easily escaped," Remulla told dzMM radio.

Calls to the governor's office and mobile phone by Agence France-Presse were not returned.

Cerbo said that 12 people were being treated for gunshot wounds in hospitals in Manila and Cavite following the rampage.

Police said that a pregnant woman and four children were among those shot and that two of the children had died.

Police said on Saturday that they still have not established the motive for the attack.

They said that Bae had been an elected member of the village council but left the community after being defeated in a 2010 ballot for the post of village chief.

Bae and Lopez, described by police as the gunman's employee, began drinking and taking the banned stimulant methamphetamine or shabu on New Year's Eve, according to Remulla.

Frequent shabu use can lead to anti-social or even psychotic behavior, said Derrick Carreon, spokesman for the Philippine Drug Enforcement Agency.

"They may start seeing demons during withdrawal. You take it from there," he told Agence France-Presse on Saturday.

Shabu is the most commonly used narcotic of nearly two million illegal drug users in the country, Carreon added.

Friday's shooting rampage followed the New Year's Eve deaths of two children by celebratory gunfire in Manila, which has triggered outrage and condemnation of the Philippines' poorly enforced gun laws.

There were 1.2 million registered firearms in the Philippines last year, with another 600,000 unlicensed weapons in circulation, according to police.