By CARLOS MARTINEZ

Two militant anti-Castro exile organizations, who joined forces less than two months ago to harass Communist Cuba, were reported Monday to have carried out their second successful air raid on the island.

Spokesmen for the Insurrectional Recovery Revolutionary Movement (MIRR) and Comandos-L claimed the two groups bombed an important Cuban installation.

The claim was confirmed by Cuba's Armed Forces Ministry. The ministry said in a communique that "an unidentified plane flying from the north" dropped three U.S.-made bombs near the Cepero Bonilla chemical plant in Matanzas, on Cuba's north coast, before dawn Sunday. All missed the target, the ministry said.

The MIRR, headed by Dr. Orlando Bosch, and Comandos-L, headed by Jose Rajoy, had claimed credit for a Sept. 29 bombing of a thermoelectric plant near the north coast of Camaguey Province.

In a joint statement Monday, Bosch, a former pediatrician with a history of clashes with U.S. authorities, and Rajoy said that a twin engine plane dropped two napalm and four explosive bombs, grenades and sprayed the area with machine gun fire.

"We have advanced in the process toward the liberation of Cuba and feel aura of victory," the two leaders said. "Commitments with heads of our organizations inside Cuba make it necessary for us to establish and orient a new policy in exile."

Bosch's latest clash with U.S. authorities took place Oct. 5, when a Naples jury found him "guilty of transportation of explosives with a recommendation of mercy." He was charged with transportation of dynamite bombs over the Tamiami Trail in April.

The Cuban doctor and another companion still have a federal court trial pending in Miami on extortion charges.