The clashes occurred late on October 23 during commemorations to mark the 50th anniversary of the 1956 uprising against Soviet rule.
Police used tear gas, rubber bullets, and water cannons to disperse protesters in several areas of the capital.
By early today, police say they arrested more than 30 demonstrators. About 10 police officers were injured.
The protesters were calling for the resignation of Socialist Prime Minister Ferenc Gyurcsany over his admission that he lied about the country's economy ahead of elections earlier this year.
(compiled from agency reports)