JOHANNESBURG, South Africa (AP) _ Six Cabinet ministers in the black homeland of Transkei resigned Thursday because of an investigation into corruption that implicated the prime minister, Transkei officials said.

For several hours, South Africa's state radio reported that Transkei's military had seized control of the nominally independent homeland and placed at least eight Cabinet ministers under house arrest. The South African Broadcasting Corp. later revised its report and said no coup had occurred.

The SABC said Prime Minister George Matanzima was outside the homeland Thursday receiving medical treatment in the city of Port Elizabeth.

Matanzima was accused last week of accepting a $500,000 bribe. The SABC report said new corruption allegations had been lodged against Matanzima on Thursday and other reports indicated he would not be permitted to continue in office.

Transkei's president, Tutor Ndamase, said a tribal chief had been given temporary command of the prime minister's office. Ndamase's position is considered less powerful than that of the prime minister.

The SABC and the independent South African Press Association said Transkei soldiers set up road blocks throughout the homeland and searched all government vehicles.

South African Foreign Minister Roelof Botha, who was visiting the African nation of Malawi, issued a statement saying Ndamase told him ''that there has been no coup,'' that no one had been detained and that the government was continuing normally.

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

Botha said he had been kept informed of events in Transkei by the South African ambassador, and ''nothing has happened to affect our bilateral relations.''

The South African Press Association said Transkei security police had banned all political meetings in the homeland through next Wednesday. Leaders of the governing National Independence Party had planned to meet Monday, and a special session of Parliament was scheduled for Wednesday, reportedly to seek Matanzima's resignation.

The South African government has come under fire recently from critics who say the homeland system is rife with corruption and mismanagement that is wasting substantial amounts of the large subsidies provided by South Africa. In 1986-87, South Africa provided more than 60 percent of Transkei's $450 million revenues.

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

The SABC said the six Cabinet ministers and two deputy ministers resigned after ''serious allegations of corruption'' involving millions of dollars. Those resigning were the ministers of agriculture, commerce, interior, transport, justice and local government.

The developments followed prolonged feuding between Matanzima, 68, and his brother, Kaiser Matanzima, who stepped down as the homeland's president in 1986.

The prime minister expelled his 72-year-old brother from Transkei's Parliament in May after the elder Matanzima accused the prime minister of corruption. The elder Matanzima, who was banished to a rural area, vowed he would try to retake power.

Transkei, which lies along the Indian Ocean between the port cities of Durban and East London, has a population of about 3.3. million, mostly members of the Xhosa tribe. It was designated as independent by South Africa in 1976 and is the oldest and largest of the four nominally independent homelands.

The four have authoritarian governments that cooperate with South Africa's government and discourage militant opposition to apartheid.

By law and custom in South Africa, apartheid establishes a racially segregated society in which the 25.6 million blacks have no vote in national affairs. The 5 million whites control the economy and maintain separate districts, schools and health services.

South Africa defends the homeland system, which includes six ''self- governing states,'' as a means of providing political rights and self- determination to black ethnic groups.

Anti-apartheid groups condemn the system as a means of depriving blacks of South African citizenship and strengthening white-minority domination.