At least 27 persons, all of them black, have been killed during the past 24 hours in South Africa's bloodiest day of violence in seven months.

Nineteen of the victims died in two mass shootings by police, one in the Bophuthatswana tribal "homeland" north of Pretoria and the other in the black township of Kwazekele, outside Port Elizabeth on the Indian Ocean coast.

This follows the death of six persons yesterday, including two policemen who were shot in Crossroads squatter camp outside Cape Town, and marks a sharp increase in the level of racial violence just three weeks after President Pieter W. Botha lifted a seven-month state of emergency.

The upsurge also comes as black activist groups prepare for a meeting in Durban over Easter that could result in the launching of a new national campaign of strikes, boycotts and civil disobedience.

The major incident today occurred when police opened fire on a crowd of 5,000 to 10,000 blacks holding a meeting on a soccer field in Bophuthatswana, killing 10 and wounding at least 70. An estimated 1,000 others were arrested.

Col. David George, a spokesman for the Bophuthatswana police, said the crowd gathered on the soccer field near a large squatter area called Winterveld "to be addressed by a speaker who never arrived." Police ordered the crowd to disperse because the meeting was illegal, George said, then opened fire to defend themselves when the crowd began stoning them.

A spokesman for an organization called the Winterveld Action Committee said the meeting was called to protest to the local police chief the arbitrary arrest of youths in the area.

The mass shooting in Kwazekele occurred last night when police took up positions inside a liquor store that had been attacked by a rioting mob, and shot dead eight blacks when the crowd returned. A ninth man wounded in the shooting died in a hospital today.

A police report said the crowd stormed the liquor store with gasoline bombs. Many liquor stores, which operate under license from the white administration, are owned by black township councilors or their relatives. They are often the targets of attack by activists, who regard such people as "collaborators" and beneficiaries of the apartheid system.

Two more black men were shot dead in Kwazekele last night when police fired on a group they said attacked their armored personnel carriers with stones and gasoline.

Clashes between residents continued in Kwazekele throughout today, with police repeatedly using tear gas and shotguns to disperse crowds they said were throwing gasoline bombs at black policemen's houses.

Two young blacks were killed in Crossroads last night when police fired on a crowd they said stoned their vehicle.

A white woman motorist was injured in the same area when she was stoned, lost control of her car and crashed. Police said they dispersed her attackers with shotgun fire, wounding a man.

At least five deaths were the result of black-on-black violence, with the victims being subjected to the "necklace" executions used against blacks that the assailants regard as collaborators with the white-minority government. A tire filled with gasoline is pulled over the victim's body and set alight.

About one-third of the more than 1,300 blacks who have died in violence since September 1984 have been killed by other blacks in this civil war against "collaborators." The other killings are attributed to police and troops.

About 1,500 delegates representing black student and community organizations from more than 600 districts, as well as the major black labor unions, are due to meet in Durban over the Easter weekend to decide whether a nationwide boycott of schools, suspended last January, should be resumed.

In a pact with community organizations and unions, black students agreed in January to end a year-long boycott and return to school on condition that the government met a series of political demands by March 31. The unions and community organizations agreed that if the demands were not met, they would support a resumed boycott with a coordinated series of protests.

Some of the demands, notably the lifting of the emergency, have been met but most have not and the conference is being called to assess what the black response should be.