WROCLAW, Poland (AP) _ A misdemeanor court Wednesday fined seven Solidarity supporters for organizing an illegal rally on the outlawed free trade union's seventh anniversary, a Solidarity activist said.

Police detained the seven Monday during a pro-Solidarity rally outside the Polar refrigerator plant in this southwestern Polish city that drew about 500 workers, said Jozef Pinior, a Wroclaw Solidarity leader who was among those held.

Pinior said he was fined the maximum $180, equivalent to about twice the average monthly salary. He said the remaining six union supporters received fines of up to $150.

The seven were released after the hearing, Pinior said. An eighth person detained at the rally was released without charges as a juvenile late Tuesday.

Pinior said he and the others had filed a complaint to the Interior Ministry protesting that police beat and mistreated them.

''I was beaten by a security policeman while I was delivering a speech at the rally,'' said Pinior, contacted by telephone at his Wroclaw apartment.

''The police were simply taken by surprise ... that a rally took place outside the factory ... obviously pointing to the fact of the existence of Solidarity, and this led to a situation in which the police action simply got out of control,'' he said.

In the nearby town of Lubin, twelve Solidarity supporters, including Wladyslaw Frasyniuk, the regional Solidarity leader, were freed Monday after a misdemeanor court fined them as much as $125 for inciting public unrest.

They were among 18 people police detained on Sunday in Lubin for trying to organize a pro-Solidarity demonstration. Six of those detained were released immediately without charges.

Solidarity supporters in several Polish cities took part in demonstrations on Sunday and Monday to commemorate the signing of the Aug. 31, 1981 Gdansk Agreement between the government and striking workers that led to the birth of Solidarity, the first free trade union in the Soviet bloc.

Parliament outlawed Solidarity in October 1982, 10 months after martial law was imposed. Martial law was lifted in July 1983.