A crowd of 20,000 black activists swamped a white suburb near the center of Port Elizabeth today to honor a white antiapartheid crusader who had died.

Huge funeral rallies have been the vivid keynote events in South Africa's black townships during the past year of racial ferment and Molly Blackburn had attended many of them.

For most whites, however, it was the first exposure to the passionate blend of grief, faith and rebellion characterizing those huge funeral rallies at which more than 1,000 victims of political upheaval have been honored by their own people and which have provided emotional energy for black protests.

Blackburn, 54, who represented the liberal Progressive Federal Party on the white-only Cape Province council, had exposed several cases of police brutality in the troubled eastern Cape Province region. She was killed in an auto accident Saturday night.

The Rev. Allan Boesak, a mixed-race theologian and a leader of the activist United Democratic Front, quickly picked up the theme in a speech of tribute: "Even in death Molly does what she has done all her life. She brings us together and she anticipates with a joy beyond words what this country can and should be."

For many of the white residents who live near the little St. John's Methodist Church in Port Elizabeth Central, the funeral was a startling experience.

Journalists in Port Elizabeth for the event said many whites seemed afraid as they saw the huge black crowd overwhelming three city blocks of their neighborhood while riot police stood by with dogs, tear-gas launchers and shotguns.

The white residents' anxiety grew as they watched black youths in the uniforms of the outlawed African National Congress put on an uninhibited display of revolutionary fervor on their very doorsteps.

The black youths jogged up and down the streets doing the toi toi, a militant dance expressing support for the ANC guerrillas, openly displayed the black, green and yellow colors of the underground organization and sang songs in praise of its leaders, Nelson Mandela and Oliver Tambo.

But gradually the whites were caught up in the crowd's exuberance, and they were drawn out onto their apartment balconies and into their gardens to watch. Some began mingling with the crowd.

An elderly white woman, apparently overcome at being hemmed in by the crowd, was helped across the packed street by a young black man wearing a T-shirt commemorating the police shooting of 20 mourners at a black funeral in nearby Uitenhage last March.

"I've never seen anything like this," said a white woman who lives near the church. "Where do all these people come from? I know it's Molly Blackburn's funeral, but isn't she a white person?"

A black preacher, the Rev. Mvume Dandala, seemed to answer the question when he said to loud applause during the service: "Molly Blackburn proved conclusively that being white does not in itself make one an enemy of the people."

Blackburn acquired her popularity in the black community through energetic civil rights campaigning during the past year of racial unrest, which has been most severe in the eastern Cape Province region where she lived.

As a leading member of the Black Sash women's civil rights organization she launched a series of campaigns to expose police brutality. She gathered sworn statements from blacks who witnessed the shooting of the 20 funeral-goers in Uitenhage in March, leading to the appointment of a judge to investigate. She forced authorities to act after she barged into a police station and saw a policeman flogging a young black man manacled to a table. She exposed the police practice of waiting in hospitals to arrest blacks injured in riots when they went there for treatment. With her doctor husband, she established a clinic where injured blacks could go for confidential treatment.

She regularly attended the big funeral rallies for victims of violence, and was given a standing ovation by a crowd of 70,000 at the funeral of those shot at Uitenhage.

Her death came as she was returning late at night from a trip to a black township 300 miles away, where she had been asked to help resolve a conflict between rival black groups. Another prominent civil rights campaigner, Brian Bishop, 51, died in the crash with her.