The new military junta freed free-lance American journalist Mary Helen Spooner yesterday after editors of two British newspapers expressed their regrets to the government.

Spooner, 28, was jailed Aug. 6 and accused of writing articles "defaming" the generals who seized power in a coup last month. She wrote for the Financial Times and the Economist, both of London, and the National Catholic Reporter. An article intercepted in Bolivia, but unprinted abroad, accused the generals of drug trafficking.

Editors J. D. F. Jones of the Financial Times and Robert Harvey of the Economist flew here Sunday to seek Spooner's release. The junta headed by Gen. Luis Garcia Meza had threatened to bring her to trial on charges of violating the stiff new press law.

Col. Luis Arce, the interior minister, told a news conference that Spooner would be released immediately. Harvey read a statement that he and Jones had signed expressing "regret before the government and people of Bolivia for the situation which has resulted from the activities of a correspondent of our organizations."

Spooner, of St. Louis, had been living in Chile and stuying under a scholarship from the Inter-American Press Association. She came to La Paz after the coup.

A U.S. Embassy officer was allowed to visit her at the Interior Ministry Friday and reported she had not been mistreated.

Opponents of the military government have said as many as 2,000 persons, including Roman Catholic priests, journalists, union officials and political leaders, have been arrested since the right-wing generals ousted the civilian government July 17.