Rhodesian black nationalist guerrillas today freed four white prisoners captured last year inside Rhodesia and handed them over to the Londonbased human rights organization, Amnesty International.

Calling the action "more humanitarian than political," the Zimbabwe Af. rican National Union (ZANU) presented the four -- two farmers, a forester and soldier -- to reporters at a press conference at the end of a special meeting of the nonaligned movement on the situation in southern Africa.

While a number of white farmers and other civilians have disappeared in the past two years of the worsening war in Rhodesia, this was the first confirmation that at least four of them were alive and well in the hands of the nationalist guerrillas. The soldier was off duty at the time of his capture.

ZANU Secretary General Edgar Tekere said the release of the four was not part of any "exchange deal" and that his group had not asked the Rhodesian government for any of its guerrilla prisoners in return.

"We don't have to make political capital out of the welfare of people," he said.

Amnesty International's deputy secretary general, Dick Oosting, said, however, "We hope it will get some response from the other side and not rest just as a humanitarian gesture. Let's hope the other side will respond likewise."

Oosting said he understood the four released here were the only white prisoners held by ZANU, which also claims to have captured many black Rhodesian police and army soldiers. ZANU is the Mozambique-based wing of the Patriotic Front, the guerrilla alliance fighting to overthrow Rhodesia's white-led government.

The four men were identified as Johannes Handrick Martins, 55, a South African captured on his farm in the Headlands area of Rhodesia May 18; John Kennerley, 18, a Rhodesian army recruit from the Beitbridge area taken prisoner May 2; Thomas A. Wigglesworth, 66, a British national taken away from his farm near the border town of Umtali Aug. 1; and James Black, 45, a British citizen captured at the Martin Forestry near Melsetter Aug. 18.

None of them was wearing a uniform or carrying arms at the time of their capture.

All four were relaxed and in apparent excellent health. They had only been informed Thursday that they were to be released today. All four said they planned to return to Rhodesia.

The description of their various experiences gave a different picture of Black, 45, a British citizen captured at ZANU guerrillas from that portrayed by the Rhodesian government which has tried to depict them as little more than "communist terrorists" and murderers of innocent white and black citizens.

At the press conference, the four men told in turn of their capture and long harrowing treks through the Rhodesian bush into Mozambique, involving in one instance a narrow escape from four attacking Rhodesian planes.

Three of the four had high praise for the behavior of the guerrillas and said they had been well treated given the circumstances in which they had been obliged to live as prisoners. The fourth, a Rhodesian government forestry official, refused to comment, implying it might compromise his civil service job.

The release of the four whites came at the end of a conference of foreign ministers from the 25 nations belonging to the coordinating bureau of the nonaligned group.