BONN, AUG. 15 -- East German Premier Lothar de Maiziere, conceding that his government has been unable to cushion the transition from communism to a market system, tonight dismissed four cabinet ministers responsible for the economy.

De Maiziere's move, which doubled as a purge of internal opposition in his five-party governing coalition, came as tens of thousands of East German farmers took to the streets to protest that the government had not helped them compete against products from West Germany.

In East Berlin's Alexanderplatz, the demonstrating farmers pelted Agriculture Minister Peter Pollack with tomatoes, then smashed the windows of his car. Eight hours later, Pollack, who is affiliated with no party but was chosen for the cabinet post by the opposition Social Democrats, was out of a job.

De Maiziere, a Christian Democrat, said he sacked his agriculture and finance ministers and accepted the resignations of his economics and justice ministers because "their efforts to improve the economy led to no success." Since the two Germanys merged their economies on July 1, East Germany has experienced rapidly rising unemployment and collapsing industries as its centrally planned economy struggled to adapt to Western ways.

East Berlin officials now expect unemployment to soar to 1.4 million by the end of the year, more than six times the estimated number of jobless workers last spring. The economic crisis has prompted the two German governments to advance completion of reunification plans from December to the currently proposed date of Oct. 15.

But de Maiziere's move tonight may lead to the fracture of his coalition well before then. The Social Democrats, whose support of de Maiziere after the March elections gave him a strong working majority, said they will decide soon whether to leave the government, a threat the Social Democrats have made four times in the last six weeks.

In addition to Pollack, the ousted cabinet members were finance minister Walter Romberg, a Social Democrat; Economics Minister Gerhard Pohl, a member of de Maiziere's Christian Democratic Union; and Justice Minister Kurt Wuensche, the only holdover from the former Communist government. Wuensche officially resigned, but he was included in de Maiziere's announcement of the dismissals.