JOHANNESBURG, SEPT. 1 -- A South African commission of inquiry today blamed police for opening fire without justification five months ago on black demonstrators in Sebokeng township, triggering a day of violence that left 12 people dead and 281 injured.

The commission report, released by Judge Richard J. Goldstone, who headed the panel, found that the police were under no threat from the crowd of 50,000. It also concluded that officers behaved in an undisciplined way and opened fire without orders to shoot.

Goldstone said he had been shocked by the "callous attitude" of some police officers who testified about the incident in Sebokeng, south of Johannesburg. They seemed unconcerned about the lethal nature of the ammunition they had used, he said.

The judge recommended that the actions of some police officers be referred to the attorney general of Transvaal province for possible prosecution. Law and Order Minister Adriaan Vlok issued a statement later saying the recommendation would be followed.

Lawyers said tonight, however, that prosecutions were unlikely because the shooting took place while South Africa was under a four-year state of emergency, lifted in June, that gave the police draconian powers to control "unrest" and indemnified them against legal action.

The Sebokeng shooting March 26 prompted the black nationalist African National Congress to call off its first meeting with the South African government in protest. The ground-breaking talks were rescheduled for May 2 after President Frederik W. de Klerk met with ANC deputy president Nelson Mandela and promised to appoint the commission to investigate the shooting.

Today, the ANC issued a statement saying the commission's findings confirmed its repeated complaints that the police use excessive violence in their dealings with blacks.

"The findings demonstrate an indiscipline, callousness and readiness to shoot on the part of the police. This reinforces the perceptions widely held by our people that the police are not a body for the maintenance of order, but a force of repression," the statement said.

The Sebokeng incident occurred eight weeks after de Klerk legalized the ANC and other black political organizations, sparking a series of mass demonstrations as blacks expressed themselves politically for the first time in decades. However, the situation was complicated by the emergency regulations, which required demonstrators to get permission from a local white magistrate to stage a march or rally.

The Sebokeng demonstrators were refused permission, but decided to march anyway. They were stopped by police at the edge of the township and there was a standoff lasting several hours. Then, according to Goldstone, a nervous junior officer opened fire with a tear-gas launcher, triggering a 10- to 20-second fusillade of gunfire, while the unit's commanding officer sat in his car.

Goldstone rejected police claims that the unit was being stoned by the crowd and had fired in self-defense. "There was no actual or imminent attack on the men in the police line," he said.

The commanding officer had not communicated effectively with his men and had given no order to shoot, the judge found. When he asked who had fired the first shot, no one stepped forward.

"There was a complete lack of discipline in the police line. This was a direct cause of the shooting into the crowd," the judge said in his report.

In a separate development today, representatives of Zulu Chief Mangosuthu Buthelezi's Inkatha Freedom Party and the ANC signed a peace agreement to end the war between supporters of the two groups that has claimed more than 3,500 deaths in Natal province over the past three years. The pact was signed after three days of talks between delegations from the two warring parties. The talks did not include either Mandela or Buthelezi. It was not clear whether the pact could be effective without the involvement of the two leaders.