Around 2,000 people on Monday took part in an anti-government street protest in Warsaw, though Polish freedom icon Lech Walesa was unable to attend because of health problems.
The demonstration was held in opposition to a monthly march carried out by governing Law and Justice (PiS) party leader Jaroslaw Kaczynski in memory of his twin brother Lech, Poland's president at the time, and 95 other people who were killed when the presidential jet crashed in Russia in 2010.
Opponents say Kaczynski uses the monthly event to mobilise supporters and attack centrist critics.
The Polish government is being probed by the European Union over perceived threats to the rule of law, and Walesa has previously questioned whether Kaczynski is seeking to turn Poland into "a dictatorship".
Surrounded by a heavy police presence, the anti-Kaczynski protesters chanted, "Lech Walesa, freedom, equality, democracy" and placed white roses on the police cars.
The 73-year-old Nobel peace laureate, who had been planning to attend the protest, announced Saturday he would be a no-show after he was taken to hospital for tests related to his high blood pressure.
But fellow communist-era dissident Wladyslaw Frasyniuk, who was arrested at an earlier anti-government protest, attended the demonstration.
"The government is afraid. It has put up a fence between it and the people," Frasyniuk said at the protest, in reference to the metal barriers installed along the avenue leading to the presidential palace.
Kaczynski for his part addressed his supporters -- numbering a couple of thousand -- saying "we can't hesitate. We can't quit the path we're on: that of the reconstruction of Polish democracy."
Shipyard electrician Walesa won the Nobel Peace Prize in 1983 for leading Solidarity, the Soviet bloc's only free trade union, and became Poland's first democratically elected president in 1990.
His boldness in standing up to the communist regime is still widely respected, but his divisive presidency earned him scorn from many Poles.