JOHANNESBURG, South Africa (AP) _ Gunmen ambushed a taxi van in a tense black township Friday, killing five passengers and prompting angry youths to build barricades of burning tires in preparation for street warfare.

The early-morning attack in Vosloorus, one of the bloodiest townships in the Johannesburg area, heralded a fresh wave of political violence as leaders finished drafting a plan to combat such black-on-black killing.

President F.W. de Klerk said he would likely unveil the plan forged with African National Congress leader Nelson Mandela next week. He said it would address socio-economic causes of the violence.

Previous efforts, including a national peace accord signed by all major parties in 1991, have failed to halt the bloodshed that has claimed 11,000 black lives in three years.

More than 1,200 blacks died last year in Vosloorus, Katlehong and Tokoza - three townships southeast of Johannesburg wracked by ambushes, drive-by shootings and street fighting.

Much of the violence stems from a power struggle between the ANC and the Zulu nationalist Inkatha Freedom Party, and Friday's attack appeared to follow that pattern.

Police Lt. Janine Smith said the attack may have been in revenge for shots fired Thursday night at a Zulu-dominated workers hostel in Tokoza. One man was injured in that incident.

Just after dawn, gunmen opened fire with AK-47 assault rifles on the taxi van carrying black commuters past a Zulu workers dormitory, killing three men and two women and wounding nine other people. Witnesses told police they saw three attackers run into the Zulu hostel.

Soldiers later surrounded the building and police raided it, arresting 13 people and seizing several AK-47s, two handguns, one shotgun, one semi- automatic weapon, one machine gun and police uniforms, said police Maj. Andre Venter.

When news of the shooting spread, gangs of youths set tires on fire to form street barricades. The South African Press Association reported two women thought to be visiting the Zulu hostel were injured by crowds.

Violence is expected to increase in the run-up to South Africa's first all- race election April 27.

The ANC is expected to win the vote and lead the country's first post- apartheid government. Inkatha fears ANC domination and refuses to support the election unless Zulus are guaranteed some form of autonomy.

Also Friday, a judicial commission blamed residents of a Zulu hostel, police and the ANC for a shooting Jan. 9 in Katlehong that killed freelance photographer Abdul Shariff, on assignment for The Associated Press.

Top ANC officials were touring the area with a media contingent when shots were fired from the hostel. ANC supporters then returned fire. Police arrived after the shooting.

The Goldstone Commission, an independent panel created to probe the causes of violence, condemned the hostel residents for firing the first shots and said police should have been present when the tour began.

The panel noted the ANC admitted failure to officially notify police of the tour, but said police should have been aware of the well-publicized event anyway.