South African police arrested 239 civil rights demonstrators today, including three prominent churchmen, during a march on Parliament protesting the killing by police of 19 blacks in eastern Cape Province last Thursday.

The protesters were marching on the legislature in Cape Town in defiance of a proclamation prohibiting outdoor gatherings. They planned to present a list of demands stemming from Thursday's shootings, in which police opened fire on a large crowd as it marched to a funeral in a black township near Uitenhage in Cape Province.

Today's protest appeared to signal a change in tactics among those in the forefront of the campaign against the government's system of strict racial segregation known as apartheid. It may mark a return to civil disobedience, which was abandoned 25 years ago.

Those arrested today were loaded into police vans and detained at a central city police station for several hours, then released on a warning to appear in court Wednesday to face a charge under the country's security laws.

Among those arrested were Allan Boesak, president of the World Alliance of Reformed Churches; C.F. Beyers Naude, the country's leading white Afrikaner dissident and general secretary of the Council of Churches; Archbishop Denis Hurley, leader of the Roman Catholic Church in southern Africa, and Sheena Duncan, president of a women's civil rights organization, the Black Sash.

All had attended a memorial service for the people killed at Uitenhage in a Methodist church across the street from a downtown police station in Cape Town.

Candles were lit at the service to commemorate the "deaths in the struggle in South Africa." Sydney Luckett, a Methodist minister who led the service, read from a declaration rejecting the official claim that the police were attacked by a mob at Uitenhage and opened fire in self-defense.

The declaration went on to list a series of demands. Among these were that the police and Army stop interfering with black funerals and stay clear of the segregated townships and that the government begin talks with black leaders.

As the service ended, Luckett announced that it had been decided to march to Parliament to present the demands to the government, but he warned that anyone who joined the march would be breaking the law.

"We are bound to be interrupted by the police," Luckett told the multiracial congregation. "I'm sure they will be waiting."

About half the congregation formed a column outside the church and, linking arms, began marching, with Boesak, Naude and Abel Hendricks, a former president of the country's Methodist Church, in the lead.

After marching two blocks, the procession was stopped by the police. As police vans began arriving, the crowd knelt in the road and sang, "Onward Christian Soldiers" and the black nationalist anthem. There were scuffles as police dragged the demonstrators to the vans and forced them in.

The use of civil disobedience as a political weapon was pioneered in South Africa during the 1920s, when Mohandas K. (Mahatma) Gandhi, who spent part of his early career here, began using what he called "passive resistance."

It was later taken up by African nationalists during the 1950s but ended abruptly in 1960, when police opened fire on a crowd of blacks who burned the passes they were required to carry and presented themselves for arrest at a police station in Sharpeville township, near Johannesburg.

Sixty-nine persons were killed and several hundred injured, and soon after that the main African nationalist parties were outlawed and driven underground.

Civil disobedience was abandoned after that. Many American visitors, recalling its effectiveness during the civil rights campaign in the United States, express surprise that it has been eschewed in South Africa.

In addition to the view that civil disobedience is not a practical option in the face of South Africa's ruthless security forces, Nobel laureate Desmond M. Tutu has suggested that the country's ruling white minority lacks a "minimum level of moral conscience" required for civil disobedience to be effective.

Today's demonstration could mark a change. Despite the tough represssion of black unrest in the ghettos, there is a growing spirit of boldness among antiapartheid campaigners amid the increasing international spotlight on South Africa.

There was minor unrest in many parts of South Africa today, and the police issued a general warning to whites not to enter black townships unless it was "absolutely necessary."

The warning, broadcast on radio and television, advised whites who had to enter the black ghettos to request a police escort.

There was sporadic unrest, and the police used tear gas several times in the troubled townships around Uitenhage and adjacent Port Elizabeth as the minister of law and order, Louis le Grange, visited the scene of last Thursday's shooting for the first time.

Police who were involved in the shooting showed him around and helped brief him for a parliamentary debate this afternoon in which his handling of the mounting crisis came under heavy attack from opposition members who conducted their own investigation at the scene last week.