Troops and police were reported tonight to be fighting running battles with young black radicals in three black townships outside Pretoria, the South African capital, coinciding with a transport strike and a planned two-week consumer boycott.

Eight more black people died in various parts of the country, according to police reports, but rioting subsided in Durban after a week of violence that has left 65 dead in and around the coastal city.

Hopes that President Pieter W. Botha might try to defuse the racial crisis by announcing concessions to the black majority, including the release of imprisoned nationalist leader Nelson Mandela, faded tonight when U.S. Rep. Steven Solarz (D-N.Y.) emerged from a meeting with Botha saying his earlier sense of optimism about the president's intentions had been deflated.

At the same time Mandela's lawyer and family denied local reports that they had been involved in negotiations about the black leader's release, and said they did not believe this was imminent.

About 1,000 students beginning a protest strike to back a consumer boycott campaign clashed with police today outside Witwatersrand University in Johannesburg as police using whips and tear gas dispersed the marchers, who included both blacks and whites, according to a university spokesman. About 30 of the students were injured and several were arrested.

Security forces, meanwhile, aided by black police in Kwathema township east of this city, conducted house-to-house searches for five hours to force boycotting students to return to classes.

In another development, in Pietermaritzburg, in Natal province, government prosecutors heard a warning from the presiding judge at the treason trial of 16 opposition United Democratic Front activists that they risked losing the case unless they could provide more explicit evidence to support their charges.

The shifting center of unrest reflects a continuing pattern of the black unrest either being repressed or burning itself out in one area, only to flare up in another. It is a pattern that has continued for nearly a year, during which the total death toll has risen to almost 600.

Pretoria, like Durban, is not oneof the 36 urban areas where the government proclaimed a state of emergency July 21. Again the pattern has been that as the mass arrests made under the emergency regulations -- which reached 1,627 today -- appear to have damped down the trouble in the designated areas, the unrest has shifted to other towns and cities outside those areas.

An exception is the eastern Cape Province, a traditional region of black nationalist militancy, where the unrest seems to have become endemic despite the toughest security force crackdown in the country. There was more trouble in that region today as activists threw gasoline bombs at black policemen's homes in Port Elizabeth's Kwazhekele township and administration offices and a school were set on fire in East London's Duncan Village township.

The failure of the emergency declaration to quell the unrest seems to present Botha with a difficult problem, according to analysts and observers.

Either he must extend the emergency, which is likely to further tarnish South Africa's international image and cause more damage to its suffering economy. Or he must enter a series of congresses of his ruling National Party, beginning Thursday, with an image among its white Afrikaner supporters of a leader who stirred up trouble by offering the country's black majority some tentative reforms and now cannot bring them under control.

Trouble began in the Pretoria townships over the weekend when, in a conflict that bore some similarities to last week's Durban clashes between Zulu tribesmen loyal to Chief Gatsha Buthelezi and more militant supporters of the United Democratic Front, migrant workers from the tribal areas clashed with students and other city dwellers.

According to people in the biggest of the townships, Mamelodi, fighting broke out after radicals killed a hostel resident whom they believed to be a police informer. Police reported tonight that "several" people had died in the fighting.

As rioting escalated, shops were looted and burned. A black reporter who lives in Mamelodi said tonight the township was like "a war zone" with deserted streets, burning buildings and groups of students fighting running battles with police and soldiers. Police reported they had shot to death a 12-year-old black girl while firing at a crowd of blacks hurling gasoline bombs at riot patrols.

Coincidental to the rioting, activist groups launched a boycott of white shops in downtown Pretoria at the weekend as a protest against the emergency declaration. The two-week boycott began Saturday and supermarkets closed early today because there were no customers.

No buses or taxis operated out of the Pretoria townships today and few black people went to work. All schools in the townships of Mamelodi, Atteridgeville and Soshanguve were closed as students began a protest boycott.

Although the unrest in the Pretoria townships has not reached the level of other major riot areas, it is seen as significant because it is occurring in the capital, which is regarded as the bastion of white Afrikaner authority and where blacks have traditionally behaved deferentially.

Reports from Durban indicated that the five-day orgy of violence was dying down, although police said they had found another four bodies in Umlazi township, bringing the death toll for the week to 65.

Armed Indian vigilante groups and members of Buthelezi's Zulu-based Inkatha movement patrolled the townhips as a kind of private security force that seemed to have the sanction of the local police.

As an uneasy calm returned to the riot-torn townships, students were reported returning to school and a meeting of 3,000 at the Asian University of Durban-Westville voted to end a boycott of lectures.