In a move likely to have far-reaching impact on news coverage of volatile southern Africa, the government of Zimbabwe barred foreign correspondents based in South Africa today from reporting in the country and asked a South Africa-based three-man television crew of the British Broadcasting Corp. to leave Zimbabwe as soon as possible.

The ban, one of a series of moves aimed at western reporters in recent months, was imposed one day after six southern African "front-line" governments agreed that they all would take the action as part of an "offensive" against what they called South Africa's campaign of "systematic disinformation."

By official estimate, the ban will prevent entry into the six nations--Zimbabwe, Zambia, Mozambique, Angola, Tanzania and Botswana--by more than 100 western correspondents who cover southern Africa from their regional base in Johannesburg. Locally based correspondents reporting to bureaus in South Africa also are banned.

"We want a total information disengagement from South Africa," a Zimbabwean government spokesman said. The policy, he added, will be applied immediately and "very, very firmly."

For the time being reporters for South African media are not affected, but the spokesman, Justin Nyoka, said the policy eventually will cover them as well, although the government will make some exceptions.

The ban especially will affect television coverage because the three major American and two British networks have no correspondents in black Africa, relying for coverage on crews from Johannesburg. The leader of the BBC crew now in Harare said he and his associates will return to Johannesburg Tuesday.

In Washington, State Department spokesman John Hughes expressed the U.S. government's "regret" at the prohibition, saying, "Our strongly held view is that no attempts should be made to restrict freedom of the press."

The front-line action means that the media will have to place correspondents on both sides of the increasingly hostile boundary between South Africa and its black neighbors, an expensive proposition, or choose to be present on only one side. Correspondents based in black Africa often have considerable difficulty in gaining entry to South Africa.

The Zimbabwean government has sharply criticized the western media during the last six months since it received unfavorable coverage over Army repression of civilians allegedly supporting dissidents loyal to self-exiled opposition leader Joshua Nkomo. Religious and relief officials protested to the government, saying that more than 1,000 civilians were killed by the troops.

One Harare-based journalist was expelled, another based in Johannesburg was barred and there were calls for the exclusion of more correspondents.

Some of the sharpest press criticism of Zimbabwe has come from British reporters, and Prime Minister Robert Mugabe often has retaliated in kind. Speaking to the Britain-Zimbabwe Society tonight, he said, "We are suffering at this point of our history from undeserved severe attacks and distortions in the British and other European media."

The Zimbabwean government has expressed satisfaction with news coverage in Soviet Bloc countries, and announced last month that it was signing contracts with the Soviet, East German and Bulgarian news agencies.

The joint policy statement of the front-line nations was hammered out at a weekend conference of information ministers at Kadoma, about 100 miles west of Harare.

Noting that South Africa is the base for most correspondents, the ministers said Pretoria has launched a "carefully orchestrated propaganda aggression" against its black neighbors.

The ministers appealed to the international media to establish regional bureaus in the black-ruled countries, and to encourage this, their statement said, they "decided that foreign correspondents accredited to South Africa and those reporting to regional bureaus in South Africa will not be allowed, in principle, to work in the front-line states anymore."

"A correspondent banned in one front-line state is deemed banned in all front-line states," they said.

Spokesman Nyoka explained that the term "in principle" was inserted to allow the countries to invite correspondents in South Africa "favorable to us."

Zimbabwe is the main southern African country covered from Johannesburg. Angola, Mozambique and Tanzania generally ban correspondents from South Africa already.

Only a few western news agencies, among them The Washington Post, maintain full-time bureaus in any of the front-line states staffed with correspondents from the home office. In contrast, Johannesburg has scores of such correspondents.