Six more blacks were reported to have died, a land mine blew up a delivery truck, and a sniper shot a white policeman in the chest, the government said, as black South Africans today recalled another emotional political milestone.

This story was written under emergency press restrictions, which strictly limit the freedom of foreign and local reporters here to gather news independently.

Today was the 31st anniversary of the adoption by black nationalists of a set of nonracial principles called the Freedom Charter, which has become the credo of present-day antiapartheid activists.

The government stepped up its security surveillance, including a house-to-house search of a sector of the black township of Soweto called Orlando East, in apparent anticipation of another wave of unrest to mark the anniversary.

At the same time it made clear that there was no possibility of an early end to the state of emergency declared two weeks ago.

The Minister of Law and Order, Louis le Grange, told a public meeting in the Transvaal provincial town of Nelspruit last night that the government was determined to apply its emergency regulations "relentlessly" and had no intention of lifting them soon.

His statement put an end to speculation that the emergency might be lifted this week and replaced by a series of regional emergencies under two new security bills that became law today.

It was the delaying of these bills by the minority Colored (mixed-race) and Asian chambers of the segregated parliament, who strongly opposed them, that led the government to declare the emergency on June 12.

Officials in Pretoria, the capital, had said they wanted to avoid such heavy-handed action because it would hurt the economy and increase the risk of international economic sanctions.

They also said they believed the critical period would be between June 16, the 10th anniversary of the 1976 Soweto uprising, and today's anniversary of the adoption of the Freedom Charter by a mass meeting of blacks in Soweto in 1955.

Local analysts said they now believe, however, that the government has been encouraged by the reluctance of its major trading partners, particularly Britain and West Germany, to apply sanctions, and has decided to continue with its efforts to curtail the black nationalist opposition.

The six people killed today brought the death toll since the emergency declaration to 67. The figure is fractionally lower than the average of five deaths a day since January. The government maintains that the crackdown has greatly reduced the level of racial and political unrest.

According to a report issued by the official Bureau for Information, the only source of authorized news under the press regulations, two blacks were shot dead while attacking police patrols in Daveyton township, east of Johannesburg, and near the coastal city of Port Elizabeth.

Three other blacks died in fighting between black nationalists and members of Inkatha, Chief Gatsha Buthelezi's Zulu tribal movement.

Another black man was killed when a shot was fired into a car near the Crossroads squatter camp outside Cape Town. The official report did not say who fired the shot.

The land mine explosion wrecked a truck near the Pretoria township of Soshanguve. The black driver of the truck was not injured, according to the information bureau.

The bureau gave few details about the shooting of the white policeman, Constable J. H. Kotze, except to say that he was conducting an investigation in the black township of Guguletu, outside Cape Town, when he was shot in the chest by a gunman concealed in a nearby house. The policeman's condition was described as serious.

In London, Amnesty International said that South African security forces had raided a black church on June 16 and detained its entire congregation, The Associated Press reported. It was the third such incident reported by Amnesty since June 12.

The group said that its information came from reliable sources in South Africa.

Amnesty said that about 70 churchgoers arrested at the Roman Catholic Church of St. Peter Claver's in the black township of Duncan Village, in the eastern Cape Province, are being held incommunicado. About 50 children were released later the same day.

A State Department spokesman said Thursday that U.S. officials were unable to confirm the arrests because of controls on information gathering.