Zambian President Kenneth Kaunda accused South Africa today of attempting to overthrow his government but he said his security forces had broken up the plot.

Kaunda made the charge at a press conference in Lusaka after Zambian authorities reportedly arrested at least 50 people, including a high-ranking military officer and several former government officials, for their alleged involvement in the conspiracy.

Kaunda accused South Africa of recruiting and training more than a hundred Zambians to overthrow his government during the night of Oct. 16. But, he said, he learned of those plans and "I instructed our boys to move in on Oct. 15."

He also accused South African troops in the territory of Namibia (Southwest Africa), which borders Zambia, of harassing Zambian security forces and supplying two boats and two ferries to help in the alleged coup.

[In Pretoria, South Africa Foreign Minister Pik Botha denied Kaunda's charges that South Africa was involved in a coup attempt against the Zambian government, Reuter reported.]

In the last few months, Kaunda has faced labor unrest with workers striking for more pay.

Amid those arrested, all within the past 11 days, are several outspoken critics of government policies, that, they say, have caused Zambia's economy to deteriorate.

These policies -- a loose form of socialism that has nationalized many industries -- and state mismanagement have become the focus of these critics' attacks since the end of the guerrilla war in neighboring Zimbabwe last December.

Kaunda's new conference follows several days of rumors about a coup conspiracy, touched off by the arrest 11 days ago of a recently promoted army officer, Maj. McPherson Mbulo, and a district governor, Rogers Mubanga.

On Oct. 15, the eve of the country's 16th independence anniversary, Kaunda imposed a dusk-to-dawn curfew and a ban on flights by private aircraft. kRoadblocks were set up on all major highways.

Those arrested included Elias Chipimo, former ambassador to Britian; Valentine Musakanya, former governor of the Bank of Zambia; Patrick Chisanga, chief of the state-run energy corporation; and Edward Shamwana, a former commissioner of the Zambian high court.

The local correspondent for the French news agency Agence France-Presse, Francois Cros, has been held for 10 days in connection with the alleged coup. fKaunda said he is being held for questioning about his alleged financing for the court defense of one of the coup's "senior leaders."

Kaunda, who has ruled the land-locked country of 5.6 million people since its independence from Britain in 1964, has been one of the West's most important partners in its efforts to seek negotiated settlements to the region's racial conflicts, especially in neighboring Zimbabwe and Namibia.

Kaunda allowed Zimbabwe guerrilla leader Joshua Nkomo to use Zambia as a base for his war against the former white minority Rhodesian government. As a result, Zambia suffered numerous attacks from Rhodesian forces seeking to destroy the guerrilla camps.

While the war was on, it was blamed for Zambia's economic hardships. But since the peace settlement in Zimbabwe, Zambians have expected an improvement in their standard of living and have been disappointed that it has not come.

This disappointment has been further fueled by the opening of the Zambia-Zimbabwe borders, which were closed during the war. Zambians have been going to Zimbabwe and returning in amazement at the flourishing economy and the well-stocked shops there, despite the war and 15 years of international economic sanctions.