Agents of the Philippines' National Bureau of Investigations found some 560 kilograms (1,235 pounds) of the substance in a Friday raid on a house and a car in Manila.

"We have been watching the house for more than a month after an informant came to authorities, telling us about the illegal drugs trade in the area," said district police chief Romulo Sapitula.

The police arrested four suspects in the car loaded with 100 kilograms (220 pounds) of suspected methamphetamine, and two more suspects in the house, who are believed to be Chinese.

The arrested men denied knowledge of the drugs, Sapitula said. Officials suspect that the drugs were likely manufactured elsewhere and stored in the house for distribution.

Cartels employ Chinese chemists

According to police sources cited by the Reuters news agency, drug cartels tend to use Chinese people as "cooks" to produce meth, which is locally known as shabu.

The Friday haul is bigger than the amount of shabu seized in the whole of 2015.

The seizure is likely to be a boon for the controversial drug war lead by President Rodrigo Duterte. His brutal push to target drug dealers and users has already claimed over 6,000 lives.

Duterte himself is under fire for admitting to killing people in the past. Earlier this week, UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein asked the Philippines' authorities to investigate the president for murder. The firebrand Duterte responded with insults and obscenities against the UN official.

dj/kms (AP, Reuters)