JOHANNESBURG, JULY 20 -- They give themselves blood-curdling names like the Order of Death, the White Wolves and the White Liberation Army and their stock in trade is terrorism -- bomb attacks at homes of white liberals, black trade union offices and public taxi stands, and grenades rolled into hotel bars late at night.

Their most notorious underground leader, Piet Rudolph, has declared "open war" on President Frederik W. de Klerk's government, the African National Congress and the South African Communist Party, promising to use scorched-earth tactics to block a handover of white power to the nation's black majority.

Some group members are reportedly hatching plots to assassinate ANC leader Nelson Mandela, de Klerk or other prominent political figures and already are conducting psychological warfare against them by sending bomb threats by telephone and fax machine.

Others have been busy stealing arms, grenades, explosives and ammunition from armories in preparation for more terrorist attacks.

White terrorism is now the most dramatic manifestation of the growing right-wing resistance to de Klerk and his reform policies aimed at ending white-minority rule in South Africa.

"I see terrorism, white and black, and nobody will have the power to stop it," said Eugene Terre'Blanche, leader of the largest of the right-wing extremist organizations, the Afrikaner Resistance Movement.

According to police statistics, 34 acts of terrorism were recorded in June -- the most reported in a single month since 1976. But only about one-fifth of the attacks were attributed to right-wing groups.

This month, white terrorists could be responsible for half of the total number of incidents. According to the police, there have been 18 acts of terrorism recorded so far in July, of which nine are believed to be the work of white right-wing factions.

Jaap Marais, head of the right-wing Reconstituted National Party said in an interview that he believed white terrorism was "inevitable" because de Klerk was acting outside his electoral mandate in legalizing and opening negotiations with the ANC and thus "inviting extra-parliamentary action."

"People contend the parliamentary fight is no longer relevant. I'm quite sure {terrorism} is going to get worse," Marais said.

Two blacks have been killed and at least 48 people, almost all blacks, have been injured in nearly a dozen bomb attacks by suspected right-wing terrorists since April, most of them in and around Johannesburg.

Police have arrested 28 whites suspected of involvement in a number of attacks and secret plots. Several were charged with illegal possession of weapons and explosives and authorities are holding at least nine under Article 29 of the Internal Security Act, used in the past mostly to lock up anti-apartheid activists.

Analysts disagree over the seriousness of the threat to de Klerk's government from the attacks. Some call it merely a public nuisance, while others fear a potentially serious problem, if a group assassinates a senior black or white leader.

Wim Booyse, a Pretoria-based political analyst for South African and U.S. companies, believes that while white terrorists represent a threat to law and order they have not yet become a danger to national security.

The prevailing view is that there are now only a small number of white terrorists, possibly as few as 80 or as many as 550, Booyse said. Booyse said he attended about 100 far right-wing group meetings early this year to assess of their activities.

Frederik van Zyl Slabbert, director of the South African Institute for a Democratic Alternative, said "the Rambo factor" in right-wing politics has to be taken seriously because many potential white terrorists are "strategically placed" in the security forces, a stronghold of employment for the 3 million Afrikaners.

"If the right wing produces a multitude of Piet Rudolphs," he said, "then we're in for a very big showdown."

Western diplomats have also expressed concern over the number of right-wing extremists skilled in the use of arms. "They are militarily trained people. They could do something that could upset the tenuous stability of right now. They could pick off a black or white leader and set off a chain reaction between whites and blacks," a diplomat said.

The liberal Afrikaans-language newspaper Vrye Weekblad succeeded in infiltrating a group of right-wingers in Boksburg, a few miles east of Johannesburg, who were allegedly plotting to hire an assassin to kill Mandela at the airport here upon his return from a worldwide tour July 18.

The police are still investigating the alleged plot and have not charged any members of the group. But the threat to Mandela's life resulted in a substantial increase in airport security measures upon his return and indicates the police are beginning to take right-wing threats seriously.

While right-wing groups say white terrorism is just getting underway, the police seem confident that they are gaining the upper hand.

Maj. Gen. Herman Stadler, national police spokesman in Pretoria, boasted in an interview that the police force "at this stage has been more successful in tracking down white right-wing terrorists than {black} left-wing terrorists."

But Stadler added: "We might have serious a problem in the future. Hopefully, the South African police can contain the situation."

The ability of Rudolph, the elusive deputy leader of the far-right Boer State Party, to evade an extensive police dragnet for months now has left many observers of South Africa wondering just how effective the security forces really are when dealing with white terrorists. Even an offer of nearly $20,000 in reward money for information leading to Rudolph's arrest has not helped to reel him in.

Rudolph has publicly admitted he broke into the Air Force Headquarters armory in Pretoria April 13 to steal a stockpile of arms and ammunition and placed a bomb May 23 at the historic Melrose House there -- site of the signing of the 1902 peace treaty ending the second Boer War with the British.

New right-wing extremist groups are multiplying so rapidly that it is hard to keep track of them. Booyse has compiled a list of 46 paramilitary and Afrikaner fundamentalist groups operating now in South Africa, many of them composed of no more than four people operating in underground cells.

One of his most interesting findings was the large percentage of English-speaking South Africans participating in terrorist activities. He has determined that 11 of the 28 white terrorist suspects arrested so far -- many of them members of the Boer Resistance Movement -- are probably of English descent and estimates that more than half of the right-wing extremists now operating are, as well.

Political fragmentation has long been a hallmark of Afrikaner politics as well as the history of Afrikaner guerrilla warfare against the British.

Terre'Blanche shrugged it off in an interview, saying: "That is what you can expect. Our history is full of it when the English tried to take over our country. But it makes it very difficult for the government to handle them {the terrorists}. It's terribly difficult to catch people when they are divided into smaller groups."