The Philippine military yesterday charged three U.S. Drug Enforcement Administration agents with murder in the killing of a Philippine colonel and two aides during an attempted drug arrest last month that ended in a bloody shootout between Philippine military and police.

DEA's acting administrator, Terrence Burke, denounced the murder charges as "totally without merit," and a DEA spokesman said none of the Americans had used weapons during the incident. Agency officials said all three agents, one of whom headed DEA's Manila office, had left the Philippines before the charges were filed and are now in the United States.

State Department spokesman Richard Boucher said the DEA agents had been working with the Philippine National Bureau of Investigation (NBI) "at the request of the Philippine government" in a joint investigation into heroin trafficking through that country. He said U.S. officials are cooperating with a Philippine investigation into the slayings.

Three members of the NBI and 10 Philippine policemen also were charged in the July 10 slaying of Col. Rolando de Guzman, who was deputy chief of the Northern Luzon Command, and two assistants, one of them a major who was his intelligence officer. De Guzman, whom DEA officials identified as a suspected heroin trafficker, was shot by NBI agents while he was allegedly selling about $10 million worth of heroin to one of the DEA agents who was posing as a drug dealer.

President Corazon Aquino has appointed a panel to make an independent investigation of the incident, a spokesman for the Philippine Embassy said in Washington. He also noted that there is no extradition treaty between the Philippines and the United States.

Aquino earlier had appointed a commission to investigate the allegations that de Guzman and other high-ranking military officers were involved in drug trafficking. The U.S. agents had been invited to testify before the commission this week and DEA officials suggested yesterday that the charges may have been placed against them to prevent their appearance.

While details remained sketchy yesterday, the murder charges, filed with the state prosecutor, shed some new light on DEA's role in a highly publicized incident that has created a major political furor within the Philippines.

According to accounts by U.S. officials, the three DEA agents were working with the NBI on an investigation aimed in part at snaring high-ranking members of the Philippine military suspected of participating in the smuggling of heroin into the United States. Although the Philippines does not produce heroin, the country has emerged in recent years as a key transit point to the United States for heroin produced in the Golden Triangle region of Burma, Laos and Thailand.

Although de Guzman was not the main target of the investigation, "he was certainly involved" in the organization under investigation, one DEA official said.

As part of the probe, Philip Needham, a DEA agent based in Thailand, was flown to Manila, and posed as a drug dealer interested in buying large quantities of heroin from de Guzman. An exchange was arranged for a shopping mall in Makati, a Manila suburb. Needham was to purchase about 20 pounds of heroin from de Guzman and then NBI agents were to arrest him.

Just what happened next remains in dispute. Police and NBI officials at the time said de Guzman and his two aides died in a shootout. However, military reports later said the three had been shot in the head at point-blank range, suggesting that the police had summarily executed them. One senior military officer referred to the killings as "cold-blooded murder."

DEA spokesman Con Dougherty confirmed yesterday that Needham was present at the shopping mall during the shootings as were the other agents charged -- Andrew Fenrich, agent-in-charge of the two-person Manila DEA office, and his deputy, Jake Fernandez. None of the three took part in any gunfire, he said.

The shootings threatened to spark a street war between police officers and the military, as angry soldiers began demanding vengeance for the slayings. The DEA agents fled the country, fearing retribution.

Washington Post correspondent Keith B. Richburg in Manila contributed to this report.