South African police shot to death at least 17 blacks today on the 25th anniversary of the slaying of 69 black protesters at Sharpeville.

Reporters at the scene estimated that more than 50 others were wounded in the industrial city of Uitenhage, in eastern Cape Province, when a contingent of 19 police officers opened fire with automatic rifles, pistols and shotguns on a crowd of about 3,000 going to the funeral of a black activist. They said that official police figures of 17 dead and 22 wounded were undoubtedly low.

In a general clampdown on black gatherings, the government had ordered that the funeral of a student killed in earlier unrest not take place today. The government feared trouble on the anniversary of the deaths at Sharpeville, a run-down township 70 miles south of Johannesburg where on March 21, 1960, police opened fire with machine guns on black demonstrators.

Black South African nationalists have never forgotten Sharpeville, and its anniversary is always tense.

Hospital spokesmen reported late tonight that a number of the injured in today's shooting were in critical condition.

Louis Le Grange, minister of law and order, told Parliament that the police were forced to open fire in self-defense when they were surrounded and stoned by the crowd, which refused to obey an order to stop what was an illegal procession.

However, a member of the funeral procession, Kelman Befile, said the mourners were boarding buses when the police arrived in jeeps and armored troop carriers and ordered them out of the vehicles.

When some began walking down the street from the bus stop, Befile said, the police opened fire.

The township of Sharpeville itself was tense but quiet today. Black students boycotted classes to mark the anniversary and put up some street barricades, but the police took no action. There were isolated clashes in other townships around the country, with the police firing tear gas and rubber bullets to disperse small groups.

The shooting in Uitenhage brought to 36 the number of black persons who have been killed in clashes with the police in eastern Cape Province in the past 10 days.

Le Grange told the white House of Assembly in Cape Town today that the shooting, which he described as "a most unfortunate incident," occurred when members of the funeral party surrounded and threatened the police officers.

"The crowd, armed with stones, sticks, petrol bombs and bricks, was marching on the highway towards Uitenhage" from the segregated black township of Langa, Le Grange said.

About one mile from a white suburb of Uitenhage the police contingent, led by Lt. Johan Fouche, confronted the procession, and the lieutenant told the marchers that their gathering was illegal. He ordered them back, Le Grange said.

The crowd ignored his order and advanced to within five yards of the police vehicles. Fouche fired a warning shot into the ground next to the leader.

"It still had no effect, and the police were suddenly surrounded and pelted with stones, sticks and other missiles, including petrol bombs," Le Grange said.

"The police officer had no alternative but to order fire in self-defense," he said.

Befile, 40, a Langa shopkeeper who was in the funeral procession, told the civil right organization Black Sash, which is investigating the incident, that mourners were lining up to board buses to take them to the funeral when the police arrived in jeeps and two armored personnel carriers -- called "hippos" by the ghetto-dwellers.

The officer in charge of the contingent ordered them out of the buses, Befile said. As the people got out, some said that if they could not ride to the funeral they would walk. They began moving down the street.

"The police jumped down from the 'hippos' and began shooting," he said, adding that there was no warning and no preliminary use of tear gas.

"The people ran," the shopkeeper added. "I ran into the nearest house. Behind me people were bleeding and crying and writhing with pain."

Eventually, ambulances arrived, he continued.

"The wounded were roughly pulled and loaded into the jeeps and ambulances with no worry for their injuries," Befile said. "Then a fire engine came and washed the blood off the road."

Chester A. Crocker, U.S. assistant secretary of state for Africa, issued a statement tonight condemning the Uitenhage shootings.

Crocker, who is on a diplomatic shuttle through several southern African countries discussing progress in his efforts to reach an independence settlement for Namibia, said in Cape Town that the shooting was "a tragic reminder of what happens when there is no basis of consent and no effective dialogue between those who govern and those who are governed."

In Washington, Secretary of State George P. Shultz told Congress that the shootings had underscored how "evil and unacceptable" the system of apartheid is, Washington Post staff writer John Goshko reported.

However, in testimony before a House appropriations subcommittee, Shultz added that he believes the United States should continue its policy of trying to maintain good relations with Pretoria and using that as leverage to press the South African government to improve the situation of the black majority.