Shouting "Soviets go home" in a third day of protests, more than 1,000 students rushed the Soviet consulate, hurling stones at the building and police.
Police using water cannons and batons dispersed the unruly crowd Thursday, which protested Soviet troop presence in Poland, said witnesses and PAP, the official news agency.At least 27 people, 20 of them police officers, were injured in unrest that spread to other parts of the city, officials said.
Cars were destroyed and benches overturned as the students put up low barricades and threw stones and bottles at police in repeated skirmishes throughout the city that also protested police treatment of demonstrators on two previous days of protests.
Representatives from the recently relegalized Solidarity trade union attempted to negotiate betwen authorities and students, many of whom were members of the Federation of Fighting Youth, a radical offshoot of Solidarity.
Authorities said the police would withdraw only after the 1,000 youths dispersed, while the protesters demanded the police retreat as a precondition.
Witnesses said the events began with a rally by 300 people from the illegal "Freedom and Peace" pacifist movement in the main square to publicize the events of the previous two days.
There are up to 50,000 Soviet troops stationed near Legnica in southwest Poland and in the northern part of the country. Authorities announced Wednesday some would be withdrawn, but did not release exact figures.
The youths, chanting "Down with communists" and "Zomo (Polish riot police) - Gestapo," staged a march under the banner of the illegal Independent Students Union.
The rally was called despite an earlier agreement with Solidarity not to conduct a third day of demonstrations. Solidarity has said the protests are harming an agreement reached with the government April 5 for democratic reforms in Poland, including elections next month.
A large police contingent blocked the way to the consulate, where the students had marched Tuesday, but some in the crowd managed to get through.
"The Soviet diplomatic post was attacked with stones," PAP said. "Attempts were made to storm the building. The law enforcement authorities which intervened were showered with stones, bottles and bricks pulled from sidewalks and the street."