Philippine law enforcers backed by troops killed four suspected Chinese drug dealers who opened fire at them during a sting operation on Monday, the national police chief said. He said more than $5.2 million worth of methamphetamines were recovered.

Police Gen. Guillermo Eleazar said the slain Chinese, who allegedly belonged to a major Chinese drug trafficking syndicate, drew pistols and shot at law enforcers who pretended to be drug buyers in a residential village in Angeles City in Pampanga province. About a dozen law enforcement and military units had shared intelligence and placed the suspects under surveillance for weeks, he said.

These are big-time distributors. We have taken down groups one after the other due to better coordination and intelligence fusion, Mr. Eleazar said by phone.

Most methamphetamines are now smuggled into the country after authorities dismantled clandestine drug laboratories nationwide, he said. The drug shipments are dropped off in the ocean and left floating off western provinces facing the South China Sea and fetched by drug traffickers onboard speedboats, Eleazar said.

Drug trafficking and addiction remain a major problem in the Philippines despite a crackdown launched by President Rodrigo Duterte when he took office in 2016.

The campaign has left more than 6,000 mostly poor suspects dead, based on police statistics, and alarmed Western governments and human rights groups.