JOHANNESBURG, South Africa (AP) _ Anti-apartheid church leaders said Friday they will play a leading role in a mass defiance campaign that is likely to intensify in the days leading up to segregated elections Sept. 6.

''The defiance campaign expresses the will of the majority of our population whilst the elections will reflect the concerns of a very small proportion of South Africans,'' the Rev. Allan Boesak said on behalf of the South African Council of Churches.

South Africa's tricameral Parliament has separate houses for the 5 million whites, 3 million people of mixed race and a million Asians, but excludes the 28 million-member black majority.

Protests began Wednesday when 270 blacks and Indians sought and received treatment at segregated white hospitals. There were no incidents despite government warnings the campaign will lead to violence.

The Council of Churches, which includes almost all leading Protestant denominations, said future protests ''will be initiated by the church, others will be supported by the church.''

Churchmen said the new protests will be launched later this month but declined details.

Its supporters hope the defiance campaign will be the largest civil disobedience action in South Africa since the 1950s. It has been organized by the Mass Democratic Movement, a loose coalition replacing the United Democratic Front, which was the country's largest anti-apartheid federation when it was banned last year.

Police made no attempt to confront protesters on Wednesday. Authorities have not said how they will respond in the future, though Law and Order Minister Adriaan Vlok said such activities ''are a time-bomb that could explode at any moment.''

Election campaigns in recent years have been marked by numerous bombings and there have been several attacks in the past two weeks in Johannesburg and Cape Town. The only fatality has been a man planting a bomb that exploded on a Johannesburg railroad line. Several other people have been wounded.

No one has claimed responsibility, but police blame the outlawed African National Congress guerrilla movement, which has called for a boycott of the mixed-race and Asian elections.

Also Friday, the church leaders condemned 16 British cricket players who have agreed to tour South Africa in 1990 and 1991.

''I think it is an obscenity for them to come to South Africa at this stage of our crisis,'' said Anglican Archbishop Desmond Tutu.

White South African sports officials have hailed the tour as a major breakthrough in the international sports boycot imposed to protest Pretoria's legal policy of race discrimination.