Thirty-seven South African church leaders and a group of white students, including some from a prestigious Afrikaner university, met this week with leaders of the country's outlawed black political movements, despite the Pretoria government's strong disapproval of such contacts.

A series of impromptu meetings took place in Harare, Zimbabwe, where all were attending a conference on South Africa organized by the World Council of Churches, it was disclosed here today.

News of the meetings has drawn sharp criticism from Deputy Information Minister D.J. Louis Nel, who issed a statement denouncing the underground movements as "organizations of terror" and warning that by meeting with them the students and church leaders might unwittingly become their instruments.

The church group included the archbishop of Cape Town, the Rt. Rev. Phillip Russell, who is head of the Anglican Church in Cape Town, and Bishop Manas Buthelezi, president of the South African Council of Churches.

They met separately with leading members of the outlawed African National Congress and of the Pan-Africanist Congress on Wednesday night and again last night, before returning to South Africa today.

Desmond Tutu, the Anglican bishop of Johannesburg and 1984 Nobel Peace Prize winner, was also in Harare for the conference and held a separate series of talks with the exiled movements.

The students, who were accompanied by a minister of the government-supporting Dutch Reformed Church, the Rev. Ben Kruger of Cape Town, met both organizations yesterday.

Five of the students were from the prestigious Afrikaner University of Stellenbosch, and four from the predominantly English University of Cape Town. In a statement issued today they characterized their discussions as "an extremely useful exchange of views on ways to overcome apartheid and bring about peace with justice in South Africa."

President Pieter W. Botha has taken a particularly tough line against Afrikaners wanting to meet with the ANC's exiled leadership, following meetings the rebels had in September with a group of top English-speaking businessmen and in October with leaders of the opposition Progressive Federal Party.

The passports of a group of eight students from Stellenbosch University were seized on Botha's orders when they revealed plans to travel to Zambia, where the congress has its exile headquarters.

When the president of Stellenbosch, Mike de Vries, made a statement mildly criticizing the government for overreacting to the students, Botha, who is chancellor of Stellenbosch, demanded a meeting of the university council to consider what he apparently regarded as an act of insubordination.

Soon afterward, seven ministers of the Dutch Reformed Church who wanted to travel to Zambia to see ANC leaders were given a formal warning and canceled their trip.

Commenting on the meetings on his return to Cape Town today, Russell said if the government wanted to prevent South Africans from meeting the "liberation movements" it would have to stop everyone from leaving the country.

Commenting on the organizations' commitment to guerrilla struggle, he said they had been driven to this by the Pretoria government's refusal to negotiate.

"How can you expect anyone to foreswear violence when we have the Defense Force and security forces in the townships?" he asked.

"The ANC and PAC do not want loss of life, but what they do want is a unified South Africa," he said. "This is where they are poles apart from the thinking of the state and many white South Africans, but completely at one with the thinking of almost all blacks," Russell added.

Tutu said it was "self-deceptive and futile" for the government to try to prevent contacts with the exiled movements at a time of crisis.

In his statement, Nel castigated the church leaders for associating with organizations committed to violence.

Stressing the ANC's commitment to revolution, Nel said: "People who conduct negotiations with the ANC . . . face the danger, without being aware of it, of becoming an instrument of these terror organizations."