The Nicaraguan Army said yesterday in Managua that it had found a set of U.S. Army identification tags on the body of a man killed while fighting with antigovernment rebels in central Nicaragua.

The Nicaraguan Army statement said the dog tags belonged to a Roger E. Patterson and gave his blood type, identification number and religion, which was Baptist.

But State Department spokesman Joseph W. Reap Jr. said later that U.S. officials had been in touch with Patterson's family in Alabama, who reported "him alive and well."

Patterson, interviewed by The (Montgomery) Advertiser, said he had served in the U.S. Army in Honduras in top secret operations near the Nicaraguan border for three months late in 1983 but had not been in Nicaragua, The Associated Press reported. Patterson told the newspaper that he still had his dog tags, the AP said.

The Nicaraguan Army said the identification tags, commonly called dog tags in the military, were found on a body following a battle March 27 between a Sandinista unit and the "Jeane Kirkpatrick Task Force" of the major rebel group, the Nicaraguan Democratic Force. The battle took place at a hamlet called Bocana de Tawa, 13 miles southeast of the town Waslala in the mountains of Matagalpa province, the statement said.

The State Department said that the U.S. Embassy in Managua "has officially requested additional information from the government of Nicaragua."

A Defense Department spokesman in Washington said a man named Roger E. Patterson, with the same Social Security number given by the Nicaraguans, served in the U.S. Army from July 1979 until November of last year. The spokesman said he had no other information on the man, although another Pentagon source said he had been mustered out of the service at Fort Rucker, Ala.

The terse Nicaraguan statement and follow-up telephone calls to Nicaraguan officials brought no explanation as to why the announcement was made more than two weeks after the incident occurred and why there was no report on the whereabouts of the body.

The report comes as the Reagan administration is pressing Congress to approve $14 million in aid to the rebels who have been fighting to overthrow the Sandinistas for three years. U.S. aid was cut off last year because of strong opposition in Congress, and the issue has become the center of a heated debate over what the U.S. role should be in the conflicts in Central America.

U.S. officials in Honduras have been extra sensitive in recent weeks to the possibility of an incident involving Americans that could jeopardize chances for a positive vote in Congress.

There was little additional information about the incident in Nicaragua. Clerical assistants who answered the telephone at both the Foreign Ministry and the Army's press office in Managua said no one was available on a Saturday to answer questions about the statement.

Defense Minister Humberto Ortega told NBC News in Managua that the body was that of a "mercenary of U.S. nationality," and added: "Once more this is evidence that the policy of the current U.S. administration is raising the amount of American blood being shed in this country." The Sandinistas call all of the rebels "mercenaries."

Indalecio Rodriguez, a leader of the Nicaraguan Democratic Force, said by telephone from Tegucigalpa, the capital of neighboring Honduras, that no U.S. citizens were fighting with his organization in Nicaragua. "There are not even any American journalists inside" with the rebels, he added.

There have been widespread reports of U.S. volunteers fighting with the Nicaraguan rebels, however. Last Sept. 1, two Americans were killed when a helicopter they were riding in was shot down over a Sandinista training camp about 20 miles inside Nicaragua. One of the Americans killed was a captain in the Special Forces of the Alabama National Guard.

The two men killed in September were members of Civilian Military Assistance, a group formed to help the anti-Sandinista rebels. Tom Posey of Decatur, Ala., a founder of the group, said by telephone yesterday that he was trying to find out if a Roger E. Patterson was a member.

"We're checking to find out," he said. "We have more than 3,000 applications." He would not say how many members of the group were in Central America, although he said "the bulk" are not.

A U.S. official in Honduras said 14 members of Civilian Military Assistance recently were expelled from that country after spending six weeks training anti-Sandinista rebels of the Indian group called Misura. The official said two U.S. diplomats traveled to the isolated base to tell the Americans that what they were doing was dangerous and if they were caught inside Nicaragua it would provide a propaganda windfall for the Sandinistas.

The U.S. official said the U.S. position is that Americans providing aid to the Nicaraguan rebels should not go into Nicaragua. He also said it is illegal for Americans to provide military training to the rebels, but they can be given humanitarian aid.