Special to The New York Times.

HAVANA, April 22--Six rebels were killed in two encounters with Government troops in Oriente Province, an army communiqué said today.

The communiqué said troops had frustrated an attempt by Fidel Castro's rebel forces to destroy the aqueduct of Santiago de Cuba, capital of Oriente Province.  Oriente is the center of revolutionary activity against the government of President Fulgencio Batista.

The clash over the aqueduct occurred at the Charco Mono Dam.  The army said four rebels were killed in the skirmish.

Two other rebels were killed when they attempted to destroy a portable electric plant near Bayamo, in Oriente, the army reported.

The communiqué also reported that three rebels were killed in Matanzas, about sixty miles from Havana, in an explosion yesterday in a small laboratory where they were making bombs.

One of the youths was Enrique Hart, 18 years old, a son of a judge of the Court of Appeals of Havana and a brother of Armando Hart, one of the leaders of Fidel Castro's revolutionary movement.  Armando Hart is now in prison in Santiago de Cuba.