Police on Saturday banned all events marking Nelson Mandela's 70th birthday and set up roadblocks around the Cape Town prison where the black leader is confined.

Hundreds of members of the security forces, many in armored vehicles, patrolled townships outside Cape Town. There were no reports of violence. Police briefly detained at least four runners in a race organized as part of the birthday celebrations.The police action came amid renewed calls from foreign governments for the release of Mandela, who is regarded by black South Africans as the country's pre-emminent black leader.

Mandela turns 70 on Monday. He has been in prison the past 26 years.

Late Saturday, police Brig. Roy During issued an order banning all events related to the birthday, including a concert that was scheduled Sunday.

Other scheduled events, including pop music concerts planned in the southeastern port city of Durban and Soweto township outside Johannesburg, were banned last week.

Police blocked off Pollsmoor Prison and said only people with "valid reasons" would be allowed near the facility.

They sealed off a sports stadium in the Cape Town township of Guguletu, forcing cancellation of a soccer game and a rugby match that were part of the birthday celebrations.

Saturday's 15-mile road race was the only one of several birthday-related events that was allowed to begin.

But a heavy police presence apparently deterred most runners from showing up at the Cape Town shopping plaza that served as the starting line.

Witnesses said police detained the only five participants after they had run less than one mile. Police said four runners were detained and later released.

The runners wore T-shirts that read, "Mandela, Freedom at 70." Two people traveling in a van alongside the runners to provide drinks also were detained, witnesses said.

More than 30 people in the Cape Town area who were involved in Mandela's birthday celebrations were taken into custody last week.

Mandela's wife, Winnie, on Friday rejected a government offer to have a six-hour visit with her husband on his birthday. It would have been the longest reunion since he was jailed.

The reunion was to have included 11 relatives of Mandela, who was imprisoned in 1962 for leaving the country illegally and inciting unrest. While serving a five-year term on those charges, he was sentenced to life imprisonment in 1964 for sabotage and plotting the overthrow of the government.

Mandela is a leader of the African National Congress, the largest guerrilla group fighting South Africa's government and its system of apartheid, under which the black majority has no voice in national affairs.

Mrs. Mandela decided to forego the special visit to focus attention on other prisoners held for anti-apartheid activities, said the family's attorney, Ismail Ayob.

Mrs. Mandela "will spend the day quietly at home, as she has on his birthday for the past 26 years," Ayob said. "She has taken this decision as both she and Mr. Mandela have never sought any special privileges for themselves."

The government, which usually grants only 40-minute visits, confirmed the cancellation.

Celebrations were planned in London and Amsterdam to mark Mandela's birthday, and several foreign governments issued messages in honor of the occasion.

Among those calling for Mandela's release were West German Chancellor Helmut Kohl, East German leader Erich Honecker, British Foreign Secretary Sir Geoffrey Howe and Canadian Prime Minister Brian Mulroney. Japan, Switzerland, Denmark, Finland, Iceland, Norway and Sweden also have called for Mandela's release.

The Italian Embassy in Pretoria said it imported a copy of director Bernardo Bertolucci's film, "The Last Emperor," because Mandela wanted to see it.

South African Information Minister Stoffel van der Merwe responded to the wave of appeals for Mandela's release by saying that "humanitarian considerations must always be weighed against the possibility that civil uprising, violence and terrorism could follow such a release."