JOHANNESBURG, South Africa (AP) _ The state-run broadcasting company said today six Cabinet members in the black township of Transkei resigned because of a corruption probe that has implicated the prime minister. It denied an earlier report of a coup in the homeland.

The South African Broadcasting Corp., on its nationally televised news program, also said new corruption allegations had been lodged against homeland Prime Minister George Matanzima. It did not say whether Matanzima, the homeland's most powerful figure, would remain in office.

Earlier today, the broadcasting corporation's radio network said the Transkei armed forces had ousted Matanzima and placed Cabinet members under house arrest.

The radio report said the overthrow occurred while Matanzima was visiting the city of Port Elizabeth, outside Transkei homeland.

Transkei residents said roadblocks had been set up on highways connecting the homeland with South Africa. There were reports that all political meetings in the homeland had been banned through next Wednesday.

The television report said Matanzima, who last week was accused of taking a $500,000 bribe, was receiving medical treatment in Port Elizabeth.

South African Foreign Minister Roelof Botha issued a statement saying homeland President Tutor Ndamase told him there had been no coup, no one was arrested, and the government was functioning.

Transkei is one of four black homelands declared independent by the South African government. No other countries, however, recognize them as separate nations.

The South African government has come under fire recently from critics who claim the homeland system has led to widespread corruption and mismanagement.

Last week, a white business consultant testified before an official Transkei inquiry commission that he had paid Matanzima $500,000 on behalf of a construction company which was awarded a $15 million contract for building 800 houses in Transkei.

The developments followed prolonged feuding between Matanzima, 69, and his brother, Kaiser Matanzima, who formerly was the homeland's president.

George Matanzima ousted Kaiser, 72, from Transkei's parliament in May after Kaiser accused the prime minister of corruption. Kaiser who was banished to a rural area, vowed he would try to retake power.

In March, about 20 white former Rhodesian commandos who had served as advisers to Transkei's army were expelled from the homeland. Following the expulsion, the military command was given to Brig. Gen. Bantu Holomisa, who was described by The Star newspaper of Johannesburg as ''a leading figure'' in today's developments.

Transkei, which lies along the Indian Coast between the port cities of Durban and East London, has a population of about 3.3. million. It was designated as independent by South Africa in 1976, becoming the first of the four nominally independent homelands.

The governments of the homelands cooperate with Pretoria's white-minority government and discourage militant opposition to apartheid, South Africa's system of racial separation and white dominance.