Arsonists firebombed early today the house and clinic of Winnie Mandela, wife of imprisoned black underground leader Nelson Mandela, in this remote farming town to which she was banished seven years ago.

Mandela, 52, who was away when the firebombs were thrown through the windows, accused the police of being behind the attack to create an atmosphere of violence around her husband to justify his continued imprisonment after 23 years.

Meanwhile, 11 more blacks were reported killed in overnight racial violence and black affairs minister Gerrit Viljoen was quoted as saying that South African whites should prepare to give up their position of "dominance," but that any reform "entails the maintenance of the principle of separate residential areas, schools, education departments and political representation."

Viljoen, who discussed proposed racial reforms in speeches to whites, said that "political reform lies ahead in which the white will exchange his former position of dominance and only decision-maker for one of a partner" in a new system "characterized by self-determination for each population group over its own affairs but coupled with coresponsibility and joint decision-making for all communities -- including the blacks -- on general matters."

At the same time, Viljoen accused the news media of creating "unrealistic expectations" about a speech President Pieter W. Botha is scheduled to give on Thursday announcing changes in South Africa's system of apartheid, or strict racial segregation.

The deaths last night and today brought the total for the past week to at least 75. Police reports said four persons died in Duncan Village, a black township near East London, where television reports showed shops and government buildings in the ghetto ablaze tonight. Four also died near Durban, where blacks and Indians have been fighting.

Trouble also broke out today in a string of small towns extending more than 200 miles north of East London, stretching police resources and underscoring the extent to which political awareness and anger has extended into previously deferential black communities in country areas.

The Institute of Race Relations estimated the total number killed in the unrest that began last September at 601, taking it past the 575 killed in the Soweto rebellion of 1976 and making it the worst wave of racial conflict in the country's history.

[Thousands of black workers from the townships of Mamelodi and Soshanguve, near Pretoria, the site of clashes Monday, stayed away from work Tuesday to protest the state of emergency imposed July 21 and the presence of police and soldiers in black townships. The strike is linked to a boycott of white-owned shops in Pretoria and a boycott of schools in the townships, The Manchester Guardian reported.]

After viewing her firebombed house, Mandela left Brandfort for Johannesburg tonight in defiance of the banishment order, claiming her life was in danger in the little town in Orange Free State.

"I will return when the government reconstructs the prison they gave me here and makes it habitable again," she said.

She faces a possible three-year prison sentence for violating the banishment order. Asked whether the government would condone her departure, Law and Order Minister Louis le Grange said tonight: "If she puts a request to me, I will give it the necessary consideration."

The burning of Mandela's house followed several attacks on the homes of black radicals and the assassination of six prominent members of the opposition United Democratic Front during the past two months. The UDF claims the attacks were the work of government agents, but others say they could be retaliation for radical attacks on blacks regarded as collaborators in the white-minority government's system of apartheid.

[Murphy Morobe, a member of the United Democratic Front's national executive who has been in hiding since the imposition of the state of emergency, emerged today to hold a press conference in Johannesburg in which he accused the apartheid "system" of responsibility for the bombing of Mandela's home, The Guardian reported.]

The home of David Gaza, chairman of the Umlazi Residents Association, which operates in one of the Durban townships that was at the center of last week's racial violence, also was firebombed early today, and in Cape Town, Allen Boesak, a Colored (mixed race) clergyman who is the foremost spokesman for the activists in Cape Province, reported to police today that he had received numerous death threats.

The inner walls of the boxy, two-room house where Mandela lived in Brandfort's run-down black sector, and of a clinic alongside where she treated people as a medical social worker, were stained an oily black from the gasoline fire. Furniture was charred, and bedding was still smoldering late this afternoon.

Cupboards had been ransacked, their contents strewn about the rooms. Medicine bottles and equipment in the clinic were smashed, and Mandela's pet kitten lay dead among the debris.

Mandela said many items of sentimental value to the family had been destroyed, including citations and awards to Nelson Mandela from many countries. A bronze bust of Robert Kennedy, presented to her during a visit by Sen. Edward M. Kennedy (D-Mass.) last January, was damaged.

Mandela was in Johannesburg when the attack took place, having been given permission to travel there for medical treatment. After flying back to see her charred house and clinic, she decided to leave again with her lawyer, Ismail Ayob.

Asked who she thought was responsible for the attack, Mandela replied: "I don't think; I know. It was the government through their security police."

She scoffed at a recent offer by Botha to free her husband, leader of the outlawed African National Congress, if he would renounce his movement's commitment to trying to overthrow white-minority rule by guerrilla struggle.

"They say he must reject violence, but they obviously haven't done so," she said, with a gesture toward the gutted buildings.