BERLIN (AP) _ East Germany may legalize the main opposition group, its official media said, and democracy marchers kept up the pressure Tuesday while Egon Krenz, the new leader, was in Moscow to see reformer Mikhail S. Gorbachev.

The ruling Communist Party Politburo held its weekly meeting Tuesday. ADN, the official news agency, indicated more leadership changes might be in store.

Several thousand people rallied in Weimar; 10,000 at Meissen, near Dresden; and 5,000 in Meiningen near the West German border, ADN reported. It said one demand of the marchers was legalization of New Forum, the largest opposition alliance.

Both the agency and state television's evening news said the Interior Ministry was studying an appeal of the ban.

In September, the Interior Ministry turned down New Forum's application for recognition, describing it as an anti-state organization, and ordered its members to cease all activity.

It has been tolerated since mass protest began several weeks ago, however, and New Forum leaders have met recently with Communist Party officials.

New Forum has attracted a wide following with its calls for free elections, free speech and a free press. It claims a membership of 15,000.

Krenz, who became Communist Party leader Oct. 18, has made moves toward reform that would have been unthinkable under his hard-line precessor, Erich Honecker.

He arrived in Moscow late Tuesday and planned to meet with Gorbachev on Wednesday. Krenz then will travel to Poland for talks with the non-Communist prime minister, Tadeusz Mazowiecki, and the Communist Party leader, Mieczyslaw F. Rakowski.

Krenz has expressed willingness to discuss reforms but also has emphasized the Communist Party's leading role.

Since he took over, authorities have made several concessions to popular demands, including granting an amnesty for thousands of people who fled the country or were caught trying to do so. It has promised eventual freedom to travel to the West.

But street demonstrations continue and many activists are skeptical, saying East Germany's leaders are only interested in reforms that do not challenge their monopoly on power.

There has been speculation East Germany's Central Committee, meeting Nov. 8-10, will purge aging Politburo members closely associated with Honecker's 18-year rule.

West Germany's Bild newspaper reported that Honecker's wife, Margot, had lost her post as education minister. The newspaper cited ''well-informed sources'' in its report.

ADN, in reporting on Tuesday's meeting of the 21-member Politburo, said the body discussed ''proposals on cadre questions'' to be considered at the Central Committee session. The word ''cadre'' applies to top-ranking party personnel.

Two Politburo members, economy chief Guenter Mittag and propaganda chief Joachim Herrmann, were removed when Honecker lost his job amid an exodus to the West of thousands of East Germans dissatisfied with his rigid rule.

Also Tuesday, ADN reported that Harry Tisch will resign after 14 years as head of the state-controlled federation of trade unions. Tisch is also a member of the Politburo. It was not immediately clear if he would keep that post.

Several trade union organizations around the country had demanded Tisch's resignation, ADN reported. It said Tisch will step down Thursday.

Many young East German trade unionists have charged that the federation has been serving only the interests of the government.