JOHANNESBURG, South Africa--Walter Sisulu, senior leader of the African National Congress and colleague of Nelson Mandela, was freed yesterday after 25 years in prison.

Four other ANC leaders from the Johannesburg area also were freed Sunday, according to associates and relatives. There was no immediate word on three other political prisoners, two of them ANC members, whose freedom also had been approved by President F.W. de Klerk on Tuesday.

Mandela, the ANC's most prominent jailed leader, remains in prison, although his release within the next few months is widely expected.

Justice Minister Kobie Coetsee and other government officials had conferred with Mandela prior to de Klerk's announcement.

Sisulu, 77, arrived under police escort at daybreak at his home in Soweto. Youths who had been waiting at the house lifted them atop their shoulders before he went inside. He made no statement.

Four other ANC leaders who had been flown to Johannesburg from Cape Town on Friday also reportedly were freed yesterday. These include three men sentenced to life prison terms in 1964 along with Sisulu and Mandela--Andrew Mlengeni, 63, Elias Mostsoaledi, 65, and Ahmed Kathrada, 60--and another ANC leader, Wilton Mkwayi, 67, who was sentenced to a life prison term in a separate 1964 trial.

Other prisoners

There was no immediate word about the status of the three other prisoners named by de Klerk--80-year-year ANC activist Oscar Mpetha, who has been hospitalized in Cape Town; Raymond Mhlaba, a co-defendent of Sisulu and Mandela who lives in Port Elizabeth; and Jafta Masemola, a member of the Pan Africanist guerrilla movement who lives outside Pretoria.

Mpetha was serving a five-year prison term for terrorism. Masemola was sentenced to life imprisonment in 1963.

On Saturday, tens of thousands of blacks in South Africa's seven biggest cities and several towns staged jubilant "victory marches" to celebrate the promised release of the eight prominent prisoners.

Organizers said never before had so many large anti-government marches been held in the country simultaneously.

Some activists had predicted a total of 250,000 marchers nationwide, but the South African Press Association put turnout at 150,000.