CAPE TOWN, South Africa (AP) _ Police used whips and dogs to disperse hundreds of blacks, including Archbishop Desmond Tutu, during mass protests Saturday at two whites-only beaches.

Tutu was carried shoulder-high onto the first beach targeted by the demonstrators and later appealed to protesters at the other beach to leave when he saw them being beaten with whips by police.

''We have proved these are God's beaches,'' he said.

The Black Sash civil rights group said several protesters sustained open wounds from the whips. The group said its monitors at the second beach ''watched with horror'' as officers charged families eating picnic lunches and used a helicopter to blow sand on them.

About 15 journalists covering the first protest, at The Strand beach east of Cape Town, were detained for two hours.

Nearer to the city, a black constable was killed by a group of youths, police said.

According to reports that local newspapers received from a human rights lawyer, four black civilians also were injured and about 35 people arrested in clashes that broke out when protesters were stopped from boarding buses to the beach. Those reports could not be confirmed.

Learning that The Strand had been sealed off with roadblocks, several hundred blacks went to Bloubergstrand, a segregated beach just north of Cape Town.

Tutu, who had strolled along The Strand beach before he and fellow demonstrators were dispersed, arrived at Bloubergstrand to see police whipping protesters.

Tutu climbed onto the back of a pick-up truck and successfully persuaded the protesters to withdrew.

John Allen, Tutu's press aide, said some white onlookers yelled insults at the archbishop.

Police also arrested at least 25 anti-apartheid demonstrators in Durban and Johannesburg, and banned a major rally that had been called for Sunday in Johannesburg to declare that outlawed opposition groups were back in operation.

Police Commissioner Hennie de Witt warned organizers of the escalating nationwide campaign of defiance that ''lawlessness and anarchy will not be tolerated.''

Leaders of the campaign announced several days ago that blacks would have a picnic Saturday on the segregated white beach at The Strand.

Late Friday, police and soldiers cordoned off a three-mile stretch of whites-only beachfront and erected signs saying the beach was closed because of a police dog-training exercise. Roadblocks were erected, and some blacks arriving in buses to join the protest were turned back.

But Tutu and about 300 other protesters reached the beach area, and the archbishop was carried onto the sand on the shoulders of some of the crowd before they were dispersed by police equipped with whips and guard dogs.

Some of the group then went to a neighboring town, Gordon's Bay, where Tutu, leader of South Africa's Anglican Church, held an impromptu news conference.

''It is incredible that the government is prepared to use arms on people who wish to have a picnic,'' he said. ''Instead of getting rid of beach apartheid, they protect it with policemen, dogs and guns.''

The detained journalists, many of them representing U.S. and British news organizations, were allowed to go free after film and videotapes were confiscated. Police said the journalists had failed to obey an order to leave the area.

In the port city of Durban, 16 activists were arrested as they stood outside a beachfront hotel protesting the presence of an international all- star rugby team. The team's five-match tour to South Africa has been approved by international rugby officials, but militants have depicted the visit as a breach of the sports boycott imposed to protest apartheid.

Police said nine people were arrested in downtown Johannesburg after scores of blacks chanted in the streets during a protest against the arrest Friday of anti-apartheid activist Mohammed Valli Moosa. Several demonstrators carried placards with the initials of the United Democratic Front, which was banned last year.

Organizers of the defiance campaign had planned several rallies on Sunday to proclaim that the anti-apartheid coalition had ''unbanned'' itself. One rally has been banned and similar action was expected against the others.

The campaign began Aug. 3, when blacks sought treatment at white hospitals, and has spread as the Sept. 6 parliamentary elections approach. The state radio Saturday said police must ''respond imaginatively'' in order to counter civil disobedience without triggering violence.