42 Killed in S. African Factional Blood Bath : Civil strife: 3 gunmen open fire on Inkatha marchers. The violence threatens to derail a peace pact.

Three gunmen opened fire on Inkatha Freedom Party supporters marching to a rally Sunday, killing 18 and touching off a blood bath at Johannesburg-area black townships in which a total of 42 people had died by nightfall.

The attacks and counterattacks marked the deadliest flare-up in months in the factional war between Mangosuthu Gatsha Buthelezi’s Inkatha party and its opponents, among them supporters of Nelson Mandela’s African National Congress.

And the violence threatened to derail a peace pact to be signed next Saturday by Inkatha, the ANC and the government. That agreement is considered crucial to President Frederik W. de Klerk’s reform program and negotiations for a new constitution.

The trouble Sunday began in Tokhoza, a dusty township 10 miles south of Johannesburg where much of the warfare of the past year has centered.

Hundreds of Inkatha supporters, most of them residents of single men’s dormitory hostels, were walking to a meeting of the regional hostel dwellers association under the guard of South African army units when a black man armed with an AK-47 rifle emerged from a house and blew a whistle, witnesses said. Then other armed men stepped from nearby houses, and they all opened fire.

Gertrude Mzizi, an official in Inkatha, and her husband turned their car around and fled, but she looked back and saw people falling to the pavement.

“They were writhing in pain,” she told the independent South African Press Assn. “Many looked to be dead. It was a terrible thing.”

Angry Inkatha members, armed with sticks and whips, returned to their hostels in Tokhoza blaming the ANC for the attacks and vowing revenge. Hundreds of police and soldiers flooded into the township in an attempt to restore order.

ANC Deputy President Walter Sisulu immediately issued a statement condemning the attack and suggested that it was carried out by provocateurs.

“We appeal to all our people to remain calm and not allow this wanton act of provocation to result in even more bloodletting,” Sisulu said. “We reaffirm our commitment to the peace process . . . and we extend our heartfelt condolences to the families” of the victims.

As the death toll mounted in Tokhoza, reaching 23, the violence spread to Soweto, the country’s largest black township. At dusk, five people were killed in the White City area of Soweto when hand grenades were thrown at a group of Inkatha-supporting Zulus returning from a meeting. The Zulus retaliated, police said, attacking local residents, killing eight.

At least six other people died in related attacks in Tembisa and Katlehong townships.

The factional violence, which has claimed more than 2,000 lives in the past year in townships around Johannesburg, appears rooted in the deep animosity between the ANC and Inkatha. But it also has elements of ethnic rivalry between Inkatha-supporting Zulus from Natal province who have come to Johannesburg in search of work and non-Zulus, many of them ANC supporters, who live in those townships.

And the ANC contends that the government’s security forces also have secretly used the ANC-Inkatha rivalry to foment, and even instigate, fighting in the hope of propping up the government’s friends in Inkatha and dividing black South Africans.

President De Klerk has denied the allegations, but since the disclosure that secret police payments were made to Inkatha last year, the president has promised to end covert support for political groups.

Factional fighting had dropped off sharply last month after high-level peace talks among the ANC, Inkatha and the government, and police had lifted dusk-to-dawn curfews in several townships.