JOHANNESBURG, FEB. 17 -- Police backed by Army troops fired tear gas at blacks protesting the eviction of rent strikers in Soweto today, according to residents and antiapartheid activists who work in the township.

The authorities confirmed that clashes occurred and that tear gas had been used, but denied reports by residents that police had fired birdshot into a crowd, wounding three persons. A police spokesman in Pretoria said an account of the incidents would be included Thursday in the daily official report on violence, and that no interim details would be released.

Police and Army troops sealed off the troubled area and prevented journalists from entering, citing emergency regulations that prohibit reporters from being within sight of security force actions.

Witnesses said some fleeing youths were chased and beaten with sjamboks, or rubber whips commonly used by the security forces, after tear gas was fired into a crowd of about 1,000 people who gathered early this morning outside the local municipal office in the White City neighborhood to protest the evictions.

It was described as one of the most serious confrontations in Soweto between black residents and the authorities since August 1986, when about 30 residents in White City and adjoining Jabavu were shot and killed in clashes that followed rent evictions.

Soweto, a sprawling black township of 2.5 million residents, was reported tense as soldiers and police in armored personnel carriers ringed White City.

Antiapartheid activists said policemen on motorcycles were patrolling the township, warning students who left their classrooms to stay away from White City. A number of residents also were reported to have stayed home from work to protest the evictions of 38 families.

A large contingent of security forces moved into the township before dawn as black municipal police began moving from house to house, demanding payment of rent arrears.

In Soweto, the country's largest black township, an estimated three-quarters of the households have refused to pay rent since June 1986 as a protest against the state of emergency and what they regard as inadequate public services.

In an effort to break the boycott, which has exacerbated the Soweto municipal government's $50 million budget deficit, authorities in November began to step up evictions, cutting off electricity to large parts of the townships and sending police to awaken rent strikers in the middle of the night.

The United Democratic Front, a coalition of groups opposed to the system of racial segregation called apartheid, condemned today's evictions, saying, "the government has created the current crisis of accommodation and land which affects millions of the {nonwhite} majority."