Cuban troops are operating in the area of southern Angola where South African forces are attacking, increasing the chances of a direct confrontation.

Five Cuban soldiers were encountered this afternoon during a tour of an area damaged by South African air raids more than 100 miles inside Angola. The number of Cubans deployed in the area could not be determined.

Angola says clashes against South African forces are still occurring only 12 miles south of Cahama, which is about 100 miles north of Angola's border with Namibia. The South Africans say they have withdrawn farther south.

Last week, Cuba issued a public warning that if the South Africans attack Cuban troop concentrations,it will retaliate.

Although my tour had been given the highest priority by the government in Luanda and I was accompanied by Angolan soldiers and a party official, the Cubans ordered us to leave the area around a burned-out village.

The Cuban officer in charge, talking in Spanish to the Portuguese-speaking troops, made hostile references to the presence of an American. After a brief argument, the Angolans reluctantly returned to their base four miles away and reported to their commander. When notified of the incident, the officer, who declined to be identified, noticeably stiffened and his face twitched.

He ordered the troops to remain at the base and drove off in his Land Rover to talk to the Cubans. Half an hour later he returned and escorted me on a tour of the village, where there was stark evidence that attacks by South African jets had hit civilian targets.

The fact that the Cuban officers were able to block the official Angolan party from entering the area, albeit only briefly, demonstrates that the claim by Angolans that the Soviet and Cuban troops in the country do not exercise any command is subject to at least occasional lapses.

On the other hand, a Swedish reporter who visited Angola a few months ago told of a case where an Angolan officer reversed a Soviet adviser who refused to let reporters see a military map.

The Cuban officer, in turning our party away from the destroyed village, said it was a military area and the civilians were not allowed to enter.

The Angolans said the American reporter had been authorized to enter, but the officer said the United States was helping South Africa to kill Angolans. It was finally agreed that the party should return to the base and check with the commander. When we returned in his company, the Cubans were not in the area.

Until now, reliable Western sources have said that Lubango, about 275 miles north of the Namibian border, has been the farthest south the Cubans have gone. Earlier this summer, leaders of UNITA, the Angolan opposition force supported by the South Africans, said Cuban troops were stationed as far south as Xangongo.

The Angolan military in the south appeared to be sensitive about the Cuban presence. I was refused permission to take a picture of a building in Cahama. The building bore a slogan in Spanish saying, "Commanders, give orders!" It is a slogan that frequently appears in Portuguese on billboards, usually along with a picture of the revered late president Agostinho Neto.

The paint was worn on the slogan, however, so it is possible that it dates from the 1975-76 period when Cuban troops helped defend the fledgling Angolan government in a civil war against guerrillas assisted by about 2,000 South African troops.