SILAY, PHILIPPINES, AUG. 2 -- Communist guerrillas freed an American Peace Corps volunteer and a Japanese aid worker today but warned Washington and Tokyo to stay out of the Philippine insurgency or risk having more of their citizens seized.

Timothy Swanson, 26, and Fumio Mizuno, 36, kidnapped in separate incidents about two months ago, were released separately by the New People's Army (NPA) during a three-day truce on the central island of Negros.

The NPA accused U.S. and Japanese aid organizations of helping the government fight the rebels, who have been battling for more than two decades to establish a Marxist state.

"The Peace Corps is a tool of the United States. It is an instrument of the Central Intelligence Agency to support counterinsurgency in the Philippines," NPA spokesman Celso Magsilang said in a statement.

"Let the arrest of Mr. Mizuno serve as a warning to the Japanese government . . . against further participation in anti-insurgency activities," Magsilang said. He added that there was not enough evidence to hold Mizuno or Swanson.

Swanson was delivered to authorities after dark, following a moonlight hike across rugged Negros hills and a river. Guerrillas armed with M-16 rifles released him to Red Cross officials, ending his 50-day ordeal.

"I am happy it's over. I'm okay, I'm okay," Swanson said before being whisked away by U.S. officials, who said he would be taken to Manila for a medical checkup. He was laughing, and walked arm-in-arm with his Filipino wife, Merle.

Swanson was taken from his home in the Negros highlands June 13, two weeks before the United States ordered the withdrawal of all 261 Peace Corps volunteers from the Philippines because intelligence reports had indicated the NPA might kill or kidnap them.

Earlier, Mizuno wept in the arms of his wife and two daughters when a 30-man guerrilla band freed him after 65 days in captivity.

"I am well," said Mizuno, who was held separately from Swanson.

Mizuno was abducted May 29 while visiting a silkworm project funded by a private Japanese aid group for which he worked as a director.