Hundreds of thousands of black students and trade unionists staged protests against South Africa's month-old state of emergency today, but large numbers of others ignored a call for national action.

Thousands of students boycotted the reopening of the country's 7,000 segregated black schools to protest the imposition of strict new security measures under the emergency.

Large numbers of blacks stayed away from work in the Johannesburg and Port Elizabeth areas, while some who did not strike held brief work stoppages.

But the labor protest appeared to have been undermined by the government's tough emergency restrictions on meetings, its detention of more than 250 union officials and its decision to release Elijah Barayi, president of the Congress of South African Trade Unions, the country's largest black labor federation.

"The state of emergency -- the legal situation, the curbs on the media, the detention of . . . trade union leaders and the fact that hundreds more are in hiding -- have combined to severely disrupt unions' ability to communicate with their members," said the Labor Monitoring Group, an independent academic research unit, in explaining today's mixed result.

The congress had called for a "day of action" to register anger over the arrest of Barayi and other labor leaders. But it did not specify to its member unions what kind of action they should undertake, and many opted for symbolic protests rather than strikes.

Congress affiliates in the western Cape Province, where emergency restrictions ban any mention of the organization in the media, decided not to take part.

Barayi was released Friday, according to Marcel Golding, spokesman for the National Union of Mineworkers, the congress's largest affiliate. Barayi, who is also a vice president of the mine union, was placed under police restrictions barring him from engaging in political activities or talking to the press, union sources said.

Less than 6,000 of the union's estimated 130,000 paid members engaged in strikes today, Golding said, compared to at least 20,000 who had staged walkouts during the past 10 days to protest Barayi's detention.

"Word of Barayi's release spread like wildfire," said Golding. "A lot of workers felt last week's strikes had achieved their purpose."

The labor protest was most effective in the industrial cities of East London and Port Elizabeth.

Thousands of Port Elizabeth blacks who reported for work dropped their tools and streamed home this morning after learning about the protest. The monitoring group said the walkout was at least 90 percent effective there.

"It was quite graphic," said a researcher for the group who asked not to be named. "By 9 a.m. there was a huge line of people walking home." He said many employers blamed the walkout on threats from young militants against those who stayed on the job.

The strike was also supported in some of the black townships around Johannesburg -- including Alexandra and the East Rand townships -- where buses and taxis did not operate and most workers stayed at home. But in Soweto, the largest black urban center, as well as in Cape Town and Durban, almost everyone reported to work as usual.

The education boycott, called by some student groups to protest measures giving educators the power to bar or expel from school any student without the right of appeal, appeared more effective.

While officials claimed that overall 80 percent of black students attended the opening day of the new term, they conceded that only 30 to 50 percent reported in Cape Province.

Many high schools in Soweto, Alexandra and the East Rand appeared virtually empty this morning, with some students trickling in as the day wore on. Contrary to expectations, there were also few police or soldiers visible near school grounds.

"The atmosphere at the majority of schools is orderly and calm," said a statement from the state Department of Education and Training, which oversees the racially segregated school system. "Pupils and teachers have reacted favorably to the introduction of safety measures."

But many students interviewed outside school grounds said they would stay away from school for at least two weeks or until the security measures are lifted.

Teachers at one Soweto school said there had been no effort today to enforce the new restrictions, which require that all students re-register and wear identity cards, and that security guards be posted at all schools.

The schools have been a prime battleground between students demanding the abolition of the apartheid system of white domination and security forces seeking to enforce order.

Many local school systems have been under boycott since 1984, when the civil unrest began that has claimed more than 2,000 lives, most of them black. Many schools have been damaged or destroyed during the violence.

The government had postponed the reopening of black schools for two weeks to implement its new restrictions, which it said would eliminate the disruptions and misuse of school facilities by "radicals."

South Africa's top school official, Minister of Education Gerrit Viljoen, warned in a speech today that funds would be shifted away from schools where violence persisted.

The state Bureau for Information, the only agency authorized under the emergency to release news on police activities and violence, reported that five persons died and a 60-year-old man was injured early Friday in an explosion at a house in KwaNdebele, the troubled black "homeland" scheduled for what is termed "independence" later this year.

The bureau also reported that two black policemen were attacked by a gang of youths outside Port Elizabeth last night. One was set ablaze and seriously injured while the second has not been found. At least 138 persons have been killed since the state of emergency was imposed June 12.

Police claimed to have saved two blacks from death by "necklace" burnings yesterday in Soweto and Tembiosa, a township outside Johannesburg.

The provincial Supreme Court in Durban heard a legal challenge to the emergency today from a black trade union seeking the release of six detained members and a ruling that the emergency was illegal. The hearing continues Tuesday.