Radicals Stage Attacks Trying to Derail S. African Constitutional Negotiations : Murders and bombings show that white and black militants could make the road to a settlement difficult unless their demands are met.

JOHANNESBURG, South Africa — With the new year just days old, South Africa is already being rocked by a new wave of guerrilla warfare from white and black radicals attempting--for very different reasons--to derail fledgling constitutional negotiations.

Since New Year’s Day, five policemen in Johannesburg-area black townships have been assassinated, apparently by left-wing black extremists, and two post offices and multiracial schools have been bombed, apparently by right-wing white extremists.

The attacks have come as a shock to many in the country, where a mood of optimism has prevailed since the successful opening round of formal negotiations among the government, the African National Congress and other political groups in mid-December.

And it is an indication that extremist groups that have chosen to sit out the talks are likely to make the road to a new constitution difficult and bloody if their demands are not met.

The most dangerous of the threats is from the right wing, which is demanding a separate homeland for the Afrikaner people, the descendants of the first white settlers in South Africa, who have run the country since 1948.

“We’re seeing the embryonic signs of the start of a (right-wing) white revolution,” said Wim J. Booyse, a political consultant in Pretoria and expert on the South African right.

“The ideological driving force is the demand for Afrikaner self-determination,” Booyse added. “And the constitutional negotiators will have to seriously reconsider right-wing demands for a separate homeland.”

Until now, right-wing violence has tended to be spontaneous and scattered. But the latest wave appears to have been well planned, with targets clearly selected for their propaganda value. That suggests a new level of coordination among right-wing militants.

Among the targets have been two multiracial schools. The Lowveld High School in the conservative rural town of Nelspruit, which was bombed with six packs of strategically placed commercial explosives on New Year’s Day, was to admit some black pupils this month for the first time.

Multiracial schools are an emotional target for the right-wing cause. Many white schools, facing closure because of declining white enrollments, have decided to open their doors to blacks. Under the government’s integration plan, parents of children in white schools may decide to open to all races, but at least half the student body must remain white.

Although the attacks have occurred late at night and have caused no injuries, the threat of further attacks is likely to discourage other white schools from becoming multiracial.

Police have vowed to vigorously pursue the right-wing bombers to prevent them from derailing negotiations.

“They will be hunted down with the same determination and ruthlessness as has been the case with (left-wing) terrorists in years past,” said Craig Kotze, spokesman for the government Ministry of Law and Order.

No organization has claimed responsibility for the blasts, but several right-wing groups maintain armed units, and numerous right-wing military cells are known to operate inside the country.

Right-wing leaders have refused to condemn the violence, saying President Frederik W. de Klerk is to blame for attempting to create a unified South Africa under black-majority rule.

Right-wing groups say De Klerk, who is an Afrikaner, has abandoned the aspirations of his people by negotiating with blacks and has ignored his promise during the 1989 election campaign never to negotiate with Nelson Mandela’s ANC. After his election, De Klerk legalized the ANC and opened talks with Mandela and other black leaders.

The threat from left-wing extremists, although unlikely to scuttle negotiations, also has the potential to make negotiations difficult for both the ANC and the government.

The military wing of the Pan-Africanist Congress, an ANC rival that has demanded that De Klerk’s white government relinquish power before beginning negotiations, claimed responsibility for killing two policemen Thursday night in Soweto. The PAC’s Azanian People’s Liberation Army told the South African Press Assn. in a telephone call that three of its soldiers had carried out the attack on a van carrying the officers.

On Wednesday, two other policemen were ambushed and killed in Kathlehong township, southeast of Johannesburg, and a third policeman, who was off duty, was killed in Soweto. During 1991, nearly 150 policemen were killed countrywide.