Almost a quarter of a century ago, four Alabamians, one a National Guard major, were killed flying a bomber against Cuba in the CIA's Bay of Pigs invasion designed to topple an unfriendly communist government in Latin America.

Last Saturday, two Americans, one an Alabama National Guard captain, were killed flying a U.S. military helicopter over Nicaragua -- raising new questions and concerns about the CIA's latest effort to topple an unfriendly Marxist government in Latin America.

"They shouldn't have been there," House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) said yesterday.

O'Neill was referring to the shooting down of a UH500 helicopter carrying Dana H. Parker, 36, of Huntsville, the Alabama Guardsman, and James P. Powell III, 36, of Memphis, both Vietnam veterans. "No Americans should be there," O'Neill said. "This should be an issue in the campaign." It took years after the 1961 incident for the U.S. government to admit publicly that the Americans were killed while flying for the Central Intelligence Agency.

This time, the government is insisting that Parker and Powell were free-lancers and were not working for the CIA or any other government agency.

But the government's story did not go over well yesterday with a number of key lawmakers, perhaps because of the Bay of Pigs and other shadowy CIA operations, including its not-so-secret war against Nicaragua's Sandinista government.

If the Nicaraguans are correct in claiming that the helicopter took off from the American-improved and -controlled air strip in Jamastran, Honduras, to join the combat operation across the border in Santa Clara, Nicaragua, a number of lawmakers reasoned, then the U.S. government cannot legitimately claim it had no responsibility for, or connection with, these first American combat deaths in Nicaragua.

Sen. Jim Sasser (D-Tenn.), who has warned about the U.S. bases in Honduras dragging Americans into Nicaragua's civil war, said yesterday that he will offer an amendment next week to the military construction bill to forbid the Defense Department from designing or building permanent bases in NEWS ANALYSIS Honduras without approval by the House and Senate. Currently, approval by the chairmen of the House and Senate Appropriations subcommittees on military construction is sufficient.

"I've strongly suspected all along that these bases were being used for other than training exercises," Sasser, a member of the Senate Appropriations subcommittee on military construction, told Washington Post reporter Helen Dewar in discussing the downing of the helicopter.

"The administration has insisted otherwise many times over," he said. "This should be conclusive proof that these bases are not being used for just military exercises only."

Rep. Ted Weiss (D-N.Y.) raised the same question about the use of U.S. bases in Honduras in a letter to CIA Director William J. Casey yesterday.

Weiss demanded "a full account of direct or indirect CIA involvement with the Americans participating in this weekend's raid."

Amid this political clamor, the Nicaraguan government moved to capitalize on the incident by restating its claims that the CIA knew what Parker and Powell were doing and that the two former servicemen were in "flagrant violation" of the U.S. Neutrality Act by participating in a combat operation against the Nicaraguan government.

"If your Justice Department knew somebody killed someone and did nothing about it, I could assume they approved of the act," said an official at the Nicaraguan Embassy yesterday. "That is the case here. These two Americans were from a group publicly committed to fight communism without the restraints they had in Vietnam. Your Justice Department has done nothing about this."

The official, who declined to be identified by name or title, said Nicaragua would return the bodies of Parker and Powell to their families and "would consider" flying the family members to Managua at government expense. He said the bodies were in a morgue in Managua.

Nicaragua's public offer to release the bodies was reminiscent of the propaganda victory Syria scored when it released Navy Lt. Robert O. Goodman Jr. to Democratic presidential candidate Jesse L. Jackson in January after Goodman and other Americans bombed Lebanon.

Back then, U.S. Marines in Beirut were trapped in another twilight zone of half-war, half-peace.