Ten persons were killed in racial violence overnight in South Africa, bringing the total to 22 since the government declared a state of emergency Thursday. Tensions increased today as the country braced for the commemoration by blacks Monday of the 10th anniversary of the uprising in Soweto, the vast black township near Johannesburg.

Police formed a cordon around the Union Building, the main executive office building in Pretoria, the capital, and authorities placed heavy guards on other government buildings and major shopping centers throughout the country in anticipation of increased violence.

In Evaton, a black township south of Johannesburg, Anglican Bishop Desmond Tutu, addressing an open-air service as white soldiers and policemen completely encircled the congregation, appealed for restraint.

"I pray that tomorrow will be peaceful and that we will observe this great day in our history with the dignity it deserves," the Nobel Peace Prize winner said.

Meanwhile, international criticism and attention were focused on the state of emergency imposed this week by the white-led government, and a U.N.-sponsored conference on sanctions against South Africa prepared to open Monday in Paris.

The West German Foreign Ministry demanded that South Africa release two German Roman Catholic priests arrested under the emergency measures, and Israel, a close ally of South Africa, said it "regards the imposition of the state of emergency in South Africa with extreme gravity." Pope John Paul II denounced the "offensive" discrimination in South Africa.

Black African leaders condemned Pretoria's moves, with Zimbabwe's Prime Minister Robert Mugabe calling for the Organization of African Unity to form a defense force to overthrow the South African government.

In Senegal, prominent African entertainers sang and danced at an all-night protest against apartheid, Reuter reported, and a highlight of the concert was a new song by Miriam Makeba called "Soweto Blues."

A massive black work stoppage is expected to bring South Africa to a standstill for the anniversary despite the arrest of an estimated 2,000 black political and labor union organizers under the tough emergency regulations.

Anxiety swept through the white community as a massive security force presence in all the major cities failed to prevent last night's car-bomb explosion outside a Durban beachfront hotel.

Two whites and an Asian in a restaurant were killed and 68 other persons, most of them white, were injured.

Official statements seem designed to reduce the level of white anxiety. Brig. Leon Mellett, a spokesman for the government's information bureau, today assured that the public would be "fully protected" during Monday's anniversary.

In an apparent reference to the planned strike, he also stressed that the government regarded June 16 as "a normal working day."

Oliver Tambo, president of the underground African National Congress, was quoted by the British Broadcasting Corporation tonight as warning that the situation in South Africa would get worse until the government released political prisoners, legalized the African National Congress and began negotiations with it.

A mass circulation progovernment newspaper, Rapport, said in an unsourced front-page article today that the government's crackdown had thwarted black activist plans to set fire to government buildings and white suburbs on the anniversary.

Grocers and butchers in some of Johannesburg's white suburbs reported that they were selling out their stocks as housewives, fearing street violence and a stoppage of deliveries to shops because of the strike, laid in supplies to last several days.

Soweto itself was quiet today, as police and troops patrolled the streets in armored personnel carriers. Small groups of young activists gathered on street corners and at one point an automobile was set on fire, but there were no clashes.

All commemorative rallies have been prohibited under the emergency regulations, but church services to mark the anniversary are planned. The authorities have said that "bona fide" religious services will be allowed but have not defined what they mean by this.

The Rev. David Nkwee, an Anglican priest who will lead one of the biggest services, advised his congregation today to come to the church in small groups of no more than two or three.

"If you form larger groups you will be tear-gassed," he warned, adding that after the service people should hurry home and not linger on the streets.

"We mustn't give the police an opportunity to shoot us," Nkwee urged.

He and other prominent figures in the community said the situation was "uncertain" following the large-scale detentions. Some expressed fears that the detention of so many leaders increased the risk of uncontrolled mob violence.

There were moments of tension in Evaton as armed police and troops surrounded the churchyard where about 300 people attended an open-air service conducted by Tutu.

The security forces withdrew midway through the service, but, before it ended, some returned and parked near the churchyard gate.

Tutu and his wife Leah, walking hand-in-hand, led the congregation out of the churchyard and past the police vehicles, one of them a big armored personnel carrier. The police took no action.

Tutu, who had a 90-minute meeting with President Pieter W. Botha on Friday that Tutu later described as inconclusive, appealed for restraint in his sermon.

Several black leaders have managed to evade the widespread detentions, which began immediately after the emergency proclamation in the early hours of Thursday and are in hiding.

The number of people detained is unknown. Estimates vary from 2,000 to 4,000, but the government is refusing to state the number or to disclose the names of detainees. Newspapers are prohibited from doing so.

The government Bureau for Information, which is now the only official source of news about the situation, has emphasized that it will give only the barest outline about detentions or even deaths.

All it disclosed about the 10 overnight deaths, apart from the three killed by the car bomb, was that four were caused by "black-on-black" violence and three by security force action.

Special correspondent Jo-Ann Bekker contributed to this report.