PRAGUE, Czechoslovakia--About 30,000 demonstrators yesterday denounced police brutality and demanded that the government and top Communist officials resign. Authorities arrested 10 dissidents but left the marchers alone.

The government denied reports that police killed a student in bloody clashes Friday, when hundreds were beaten, tear-gassed and attacked by dogs in the largest demonstration in 20 years.

Yesterday's rally began with a few thousand protesters gathering on downtown Wenceslas Square, but the crowd grew to 30,000 as demonstrators reached Narodini Street, where white-helmeted riot police beat demonstrators Friday.

"We don't let you murder us!" the crowd chanted. They also chanted such slogans as "write truthfully," "free unions" and "Jakes to the dustbin."

Milos Jakes is the hard-line leader of the ruling Communist Party and, unlike other East bloc leaders, has resisted reforms orchestrated by Soviet President Mikhail S. Gorbachev.

Jakes is joined in his intransigence by Nicolae Ceausescu, Romania's leader.

About 2000 demonstrators split away and crossed a bridge over the Vltava river in an apparent attempt to reach the hillside presidential residence.

Police did not interfere in the march but did block access to the hill. The smaller group eventually returned to Narodni Street, from where some 10,000 streamed back into Wenceslas Square.

Those arrested included Petr Uhl, a leading human rights activist, who was charged in connection with the spreading of news about the alleged death of Martin Smid at police hands Friday. The state news agency CTK said he was charged with "the crimes of harming the interests of the republic abroad and spreading alarming news."

Uhl, a veteran member of the Charter 77 group, is associated with VIA, a dissident news service active in several East European countries. If convicted, he could be sentenced to 34 years in prison.

Dissident sources in Prague and Vienna told The Associated Press that police also arrested Drahomira Drazska, who said she was Smid's girlfriend. She claimed he was killed by red-bereted special police Friday.

Some prominent dissidents such as Hana Marvanova of the Independent Peace Association, Emanuel Mandler of the Democratic Initiative and Anna Sabatova, a senior member of Charter 77, also were arrested, the sources said.

Protests also took place in at least eight East German cities yesterday and in the Bulgarian capital, Sofia. As in Prague, the demonstrators demanded democratic reforms but also punishment of recently ousted leaders--Todor Zhivkov in Bulgaria and Erich Honecker in East Germany.

Plainclothes police in Prague prevented several reporters from attending a scheduled news conference on the Smid case in the home of Charter 77 spokesperson Dana Nemcova.

According to dissident sources who spoke on condition of anonymity, police picked up some of the arrested people as they left or sought to enter Nemcova's apartment.