MEXICO CITY (AP) _ Cuban troops on alert for enemy planes accidentally shot down one of their own aircraft in southern Angola, killing a brigadier general and 25 other military personnel, the Cuban military said Thursday.

The Cuban news agency Prensa Latina, in a dispatch monitored in Mexico City, quoted a military communique as saying the ''error of Cuban rocket defense'' took place Wednesday morning as the AN-26 transport plane approached the airport at Tchamutete.

The Cuban plane's trip had been announced previously.

The airport's anti-air defense was on a high state of alert because several enemy planes had been spotted in the area, the news agency said.

The communique said that one of the rocket installations on alert fired on the plane as it approached.

Thousands of Cuban troops are in Angola helping the Marxist government fight an insurgency backed by the United States and South Africa.

The general who was killed was identified as Brig. Gen. Francisco Cruz Bourzac, the deputy minister for armaments and technology. He also was a member of the Cuban Communist Party's Central Committee and a hero of the thwarted Bay of Pigs invasion of Cuba in 1961, the news agency said.

It said that Col. Jorge Izquierdo Quinones and a group of anti-aircraft specialists headed by Lt. Col. Carlos Camilo Alvez also were traveling on the plane.

Ministry communiques on the fighting in Angola are rarely carried by Prensa Latina.

Prensa Latina reported in January that about 40,000 Cuban troops are in Angola.