Racial violence erupted in a previously untroubled part of South Africa today after authorities served eviction notices under a population resettlement program that supposedly was on hold pending review.

Police opened fire with shotguns, killing four people, as an angry crowd rioted in the segregated sector of the small eastern Transvaal town of Leandra, local sources said. They added that three of the dead were teen-agers, including a 13-year-old girl. The police reported three deaths.

Until today, Leandra was one of relatively few towns still untouched by the racial violence that has racked South Africa for 15 months.

The incident is seen here as illustrating how the large state bureaucracy that administers black affairs often aggravates racial tensions with rigid application of apartheid laws even when the government itself tries to be flexible.

Nine months ago, the government suspended its program of forced population removals in the face of an international outcry. It announced that the policy was to be reviewed.

A number of people living in the black township outside Leandra, who were scheduled for removal to the tribal "homeland" of KwaNdebele, were among those who figured in this reprieve.

Last week, 20 residents were served with eviction notices. A spokesman for the government agency that issued the notices said today that the 20 were illegal squatters who had moved in after the suspension of forced removals, but Abel Nkabinde, a community leader who heads an organization called the Leandra Action Committee, insisted in a telephone interview that they were all old residents.

According to Nkabinde, residents held a meeting last night at which they decided to stay away from work today and seek clarification from the authorities on the eviction notices.

Army trucks began moving into the town during the night, sparking rumors in the black sector that a forced removal was imminent.

As tensions rose, young blacks patrolled the streets early this morning, preventing buses from coming in to the township to take commuters to work. Police said they opened fire when a large crowd threw gasoline bombs at a state-owned beer hall and at the homes of black councilors who help administer the township.

Violence continued in the white corridor between the nominally independent Transkei and Ciskei. Another black man was killed and five were injured by police gunfire in the corridor's principal town of Queenstown, bringing the casualty toll there to 10 dead and 30 wounded since Sunday, according to police reports.

Meanwhile, 1,800 striking black nurses and auxiliary workers have been dismissed at Soweto's Baragwanath hospital. The Army has been called in to run the huge facility, which serves a black population of nearly 2 million in the Johannesburg area.

Trouble broke out at the hospital Friday when police clashed with auxiliary workers striking for more pay, leading to a riot and the arrest of more than 800 workers. Police also clashed with student nurses demonstrating against an 8 p.m. curfew in their residences.

Five hundred doctors and other senior medical staff threatened today to take protest action if the fired staff were not reinstated.

The police have used new press restrictions proclaimed two weeks ago to bar reporters from the hospital. One doctor, who did not want his name disclosed, told reporters today that he had seen soldiers rounding up 300 of the fired workers and forcing them at gunpoint to collect their dismissal pay, which they earlier refused to accept as an act of protest.

Winnie Mandela continued to defy a police order that she return to banishment in Brandfort. She had been confined there since 1977 but was allowed to visit her husband Nelson, jailed leader of the African National Congress, when he was in Cape Town for a prostate operation.