Thousands of Poles are marching through Warsaw demanding free courts and respect for the constitution and denouncing a populist government that they accuse of eroding democracy.

During the "March of Freedom" on Saturday, many people carried Polish and European Union flags and chanted slogans including "Constitution!" and "Free courts!"

Two pro-European and centrist opposition parties, Civic Platform and Modern, were the key organizers of the protest. In speeches, their leaders accused the ruling right-wing Law and Justice party of eroding democratic freedoms with an overhaul of the court system that gives the party vast powers over the courts.

The protesters' view is also supported by EU leaders, who have been urging the Polish government to reverse some of the changes.

Some protesters held up small copies of the Polish constitution.