Top church leaders from four continents meeting in Harare, Zimbabwe, called on the international community yesterday to impose economic sanctions against South Africa to force it to abandon apartheid.

Meeting in an emergency session summoned by the World Council of Churches, the church leaders also demanded that the white minority government resign.

They described resignation as "the most appropriate and least costly process of change."

"In this moment, pregnant with possibility, we agree that the apartheid structure is against God's will and that the government has no credibility," they said.

The delegates also called for the lifting of a ban on South African black guerrilla movements, a return of all exiles, the lifting of a state of emergency and the transfer of power to the black majority.

The three-day meeting, which ended yesterday, was attended by 85 church leaders, including 37 from South Africa.

They had been summoned by Emilio Castro, general secretary of the WCC.

Leading clergy from Western Europe, Canada, the United States, Australia and several African states also attended the meeting, held to determine the best ways to help South African churches in their fight against apartheid.

In a joint declaration issued at the close of the three-day conference, the church officials called on the international community to stop bank loans to the South African government, banks and corporations.

They urged churches throughout the world to support South African liberation movements and to observe June 16, the anniversary of the outbreak of 1976 riots in which more than 500 blacks died in South Africa, as a world day of prayer.

The churchmen demanded immediate implementation of U.N. Resolution 435 calling for independence of South African-ruled Namibia (South West Africa).

They also welcomed the formation a week ago of a super trade union federation in South Africa committed to fighting apartheid.

The church leaders said they believe the "moment of truth" has come to resolve the South African racial conflict, which has claimed more than 930 lives in the last 22 months.

"We have heard the cries of anguish of the people of South Africa, trapped in the oppressive structures of apartheid," they declared.

In the South African delegation was Anglican bishop of Johannesburg Desmond Tutu, a vocal critic of apartheid, and Bishop Manas Buthelezi, president of the South African Council of Churches.

Opening the conference, Zimbabwe President Canaan Banana, who is an ordained United Methodist clergyman, said it was the duty of Christians to "find ways of stopping the violence of the regime and promoting dialogue between the government and genuine representatives of the people" of South Africa.

Banana, who had been detained by the then-ruling white authorities in Zimbabwe's liberation war, warned church officials not to be "hoodwinked or used by the puppets who may wear black skins and white collars, but act as agents of imperialism or colonialism."

He was scathing in his criticism of the support he said President Reagan and the United States has given to the apartheid regime in Pretoria.

He said without U.S. and other Western support, apartheid would have collapsed long ago.

Attending the conference from this country were top officials of the Episcopal, American Lutheran, Association of Evangelical Lutheran, Progressive National Baptist, African Methodist Episcopal Zion, Presbyterian, Christian Methodist Episcopal, United Methodist Churches, the United Church of Christ and the National Council of Churches.