JOHANNESBURG, FEB. 25 -- The outlawed African National Congress guerrilla movement vowed today to step up its armed campaign against white minority rule in South Africa in response to the government's clampdown on major organizations opposed to apartheid.

At the same time, a number of leading antiapartheid activists went into hiding to avoid being served with orders restricting their movements and political activities.

Security police yesterday served restriction notices on seven black nationalist leaders, including the copresidents of the United Democratic Front (UDF) coalition, and said banning orders would be served on at least 11 more persons.

The government decreed yesterday that all but routine "administrative" functions of 17 antiapartheid groups are prohibited, and announced that the country's largest labor federation, the Congress of South African Trade Unions (COSATU), will be prevented from conducting political activities.

Citing the country's state of emergency, President Pieter W. Botha empowered Law and Order Minister Adriaan Vlok to prohibit "any activities or acts whatsoever" by any organization he named. Vlok used the power immediately to curb the 17 black activist groups.

Thabo Mbeki, the ANC's director of information and a senior member of its national executive committee, said that the guerrilla movement had no recourse except to intensify military action inside South Africa.

"The regime, in practice, is saying that peaceful, political struggle is impermissible. This pushes people to the position, given the continuation of apartheid, where the only way to do it is to take up arms," Mbeki said in a telephone interview from London.

While the ANC has not abandoned violence as a strategy since the organization was outlawed and forced into exile in 1960, it has shifted its emphasis recently toward achieving international diplomatic recognition. At the same time it is trying to broaden its following among liberal whites in South Africa.

According to government statistics, the number of ANC attacks and infiltrations from neighboring states has declined sharply in the last year.

The ANC executive committee, in a statement issued by its headquarters in Lusaka, Zambia, declared that the banning orders "vindicate our often repeated conviction that only a mass movement, uniting in its ranks the broadest front of democratic and patriotic forces and employing a multipronged strategy that includes revolutionary violence, can dislodge the apartheid regime.

"The ANC calls on the people of South Africa to rise to this new challenge as never before by adopting a posture of resistance and defiance to the tyrannical measures of the racist ruling circles," the statement added.

The government said today it would not release the names of restricted individuals, although it is known that orders were served on UDF leaders Archie Gumede and Albertina Sisulu. They are banned from working for the UDF, writing articles, giving speeches or granting interviews.

Others include Jabu Ngwenya, an official of an organization seeking the release of imprisoned ANC leader Nelson Mandela, and Simon Goubule, a UDF member and vice president of the South African Council of Churches.

Some influential white business leaders today added their voices to the mounting condemnations of the government's action.

The Chamber of Mines, which represents the country's largest mining companies, said, "Threats to law and order posed by these organizations could be adequately addressed through the due process of law."

Gavin Relly, chairman of the giant Anglo American Corp., called the measures "steps away from the rule of law."

Antigovernment demonstrations were held on several campuses, including that of Johannesburg's University of the Witwatersrand, and the South African Council of Churches called for nationwide protest services.

{In Washington, Rep. Howard E. Wolpe (D-Mich.), chairman of the House subcommittee on Africa, called the decree an "outrage" and "shocking," and said the committee will begin hearings March 15 on proposals to strengthen economic sanctions against South Africa.

{The European Community, France, the World Council of Churches in Geneva and British opposition politicians also issued statements condemning the government's action, Reuter reported.}