The mayor-elect of Johannesburg's segregated black township of Soweto, Edward Manyosi, was assassinated early today by black militants, bringing to eight the number of township councilors who have been killed during the past three months of violence in the ghettos.

As violence within the black community continued, leaders of the Catholic Church in South Africa today released a report by a special research team documenting 41 cases of alleged police atrocities, including murder and rape, said to have been committed during action to quell the township disturbances. An archbishop said a "kind of a state of war" exists between police and the people of the townships.

The two developments illustrate the complex nature of South Africa's latest spate of unrest. At one level, black militants are waging a war against other blacks who are seen as collaborating with the white minority government because they hold office in councils established under its segregationist system called apartheid. At another, the police have intervened, ostensibly to protect the "moderates" from the "agitators," clashing violently with large numbers of demonstrators. An estimated 150 people have been killed and 1,000 injured, the great majority in clashes with the police. More than 3,000 have been arrested, a third of them -- including prominent black political and labor union leaders -- under special security laws that permit indefinite detention without charges. In presenting the church report, Archbishop Dennis Hurley of Durban, president of the Southern African Catholic Bishops' Conference, said the church recognized that it had been necessary for the police to protect innocent people from "criminals and hooligans," but added that they had gone beyond that to a point where "a kind of state of war has developed between the police and the people in the townships."

Manyosi was gunned down at 1 a.m. as he sat in the back of his car with an armed guard beside him. It was only hours after he had been chosen by his Sofasonke Party to be Soweto's next mayor.

Manyosi was chosen after the previous mayor, Ephraim Tshabalala, resigned, one of many township councilors to do so since the killings began.

The government established elected councils to run the townships last year as part of a program to change the apartheid system. The elections were boycotted by most blacks, who see the changes as tokenism.

In presenting the Catholic Church's report alleging police atrocities in the townships, Hurley risks being prosecuted under a special law protecting the police from false accusations. Anyone charged under this law must prove his innocence.

Hurley already faces a charge under the special police law following the publication of a similar report by the Southern African Bishops' Conference two years ago, alleging atrocities by the South African Army and a special police anti-insurgent unit in the war against black nationalist guerrillas in Namibia.

He is due to stand trial on this charge, which provides for imprisonment without the option of a fine, Feb. 18.

The report released today was based on testimony that had been given in sworn affidavits, and about half the informants had been cross-questioned by a lawyer to test their truthfulness, Hurley said. Names of those giving the affidavits were not released in order to protect them.

A statement issued tonight by police headquarters in Pretoria said the church report contained "untruths as regards details, chronology and events."

In summarizing the impact of the evidence gathered by the church, Hurley said, "The mood of the police seems to be that the black people are our enemies and that we were out to impose our will on them by any means possible," suggesting that this attitude further aggravated the cycle of violence in the townships.

Black as well as white police officers were involved in the atrocities, according to the report.

Asked which of the 41 cases of atrocities and other police abuses cited in the report he considered the worst, the archbishop referred to one case alleging that a youth was shot dead in cold blood while in police custody, and another alleging that two black teen-age girls were arrested and raped in a police armored personnel carrier.

According to the report, four witnesses have made sworn statements about the shooting of the youth, Jacob Moleleki, whose age is not given.

They said they had been arrested Sept. 23 with Moleleki and 29 others at a funeral of a victim of the clashes, kept in prison for five days, then taken to a police station in Sebokeng township, south of Johannesburg.

While they were waiting in a police van, a young police officer entered the van and angrily demanded his coat. The youths denied having taken the officer's coat, but he drew a gun and shot Moleleki in the forehead at point-black range, the report said.

In the other case, two girls, 15 and 16, signed affadavits saying they were arrested in a Sharpeville street on the afternoon of Nov. 21 and kept all night in the armored vehicle. Two police offiecrs raped them three times, they said. A father told how his 10 year-old son, Samson Mgubdlwa, was killed by a rubber bullet when police opened fire in the family's home.