Several hundred Cuban troops are reported to have mysteriously flown to Nicaragua in recent weeks but there is no clear indication that they are ultimately headed to El Salvador, State Department sources said yesterday.

Intelligence reports of the troop movements, which are still not considered confirmed, were closely held to a small group of officials here until publicized by columnists Rowland Evans and Robert Novak in Monday's editions of The Washington Post, the sources said.

Their account said the reported arrival of 500 to 600 Cuban special forces troops "may be aimed at setting up a revolutionary Marxist government in eastern El Salvador." The columnists' account suggested that the destruction of an important bridge over the Lempa River in El Salvador was the work of the Cuban troops.

Among U.S. officials dealing with Central American affairs, the working assumption is that the mission of the Cuban forces is more likely to deal with the deepening dissention within Nicaragua than with the struggle in El Salvador, according to the sources. The initial belief was that the troops were intended to shore up Sandinista leader Daniel Ortega in the growing factional strife, sources said.

The intelligence reports are said to have described the arriving troops, coming by air from Havana to Managua in the middle of last month, as members of Cuban President Fidel Castro's special guard attached to the Ministry of Interior.