JOHANNESBURG, South Africa (AP) – An estimated 800,000 government workers demanding higher pay and more benefits walked off the job Thursday in what union leaders called the biggest strike in South African history.

Police officers, prison guards, nurses and other “essential” government workers were prohibited from striking, and the government threatened to fire anyone who joined in.

Tens of thousands of workers marched peacefully in Pretoria, Cape Town, Durban and other cities to press their demands for a 7 percent pay raise, medical insurance, a housing allowance and a plan for long-term salary increases.

The government has offered a 6 percent raise with a 1 percent performance bonus.

Leaders from eight public service unions threatened to extend the one-day strike into next week if the government did not meet its demands.

The strike brought much of the government’s work to a standstill and prompted officials to close some schools.

“This will be the largest strike in South African history,” predicted Willie Madisha, president of the Congress of South African Trade Unions. About 400,000 government workers walked off the job in 1999 in the last major strike by public employees.

The unions rejected the government’s final offer Thursday night. Public Service and Administration Minister Geraldine Fraser-Moleketi said the government could not afford to increase its final offer.

More than 20,000 strikers marched in Pretoria to the Treasury and to the Union Buildings, the symbol of political power in South Africa. At least 20,000 strikers marched on Parliament in Cape Town and another 20,000 demonstrated in Durban.

The government said Thursday its Public Service Coordinating Bargaining Council, the agency charged with resolving public service disputes, will meet Friday to try to break the impasse.

AP-ES-09-16-04 1004EDT