The kingdom of Lesotho announced today that by arrangement with the United Nations, and under pressure from this country, 22 black South African refugees living there will be evacuated to other countries.

The 22 are leaving voluntarily after South Africa imposed a partial border blockade on Lesotho, which it surrounds, in an attempt to force it to stop giving sanctuary to refugees, Foreign Minister Evaristus R. Sekhonyana said.

The refugees are expected to fly Saturday to Maputo, Mozambique. From there some will go to other African countries.

An informed source in the Lesothan capital of Maseru said by telephone that arrangements were being made for another 200 refugees to leave in later stages, but officials would not confirm this. The Pretoria government has been trying to force out the refugees, charging they are really insurgents of the banned African National Congress, which is trying to overthrow white minority rule in South Africa.

South Africa says the congress uses the black-ruled country as a launch pad for guerrilla attacks, but Lesotho denies this, saying it gives sanctuary to refugees from South Africa's segregationist system known as apartheid.

Last December, South Africa mounted a military raid on what it said were guerrilla enclaves in Lesotho.

Since then, South Africa has imposed increasing economic pressures, including a go-slow at all border crossings that has brought the landlocked country to its knees.

South African ports have also embargoed imports to Lesotho of weapons, which it says are needed to counter an increasing insurgency. A month ago, Sekhonyana said his country could no longer stand the economic "stranglehold," and would have no choice but to start evacuating the refugees.

Today, a spokesman for Sekhonyana said South Africa had presented 68 names, 24 of them unknown to the Lesothan government and another 22 of whom had left the country. The remaining 22 had volunteered to leave, he said, "in appreciation of the efforts that the Lesotho government and the citizens of this country have in the past undertaken on their behalf."

Another informed source said they did so after the government warned them it would be unable to protect them in the event of another raid. This source also said South Africa had demanded the eventual removal of "all politically affiliated refugees" and that there were 502 in this category.

In Cape Town, South African Foreign Minister R.F. (Pik) Botha declined to say whether the border restrictions would be lifted, but described the steps being taken by Lesotho as "constructive."