Police have warned demonstrators that gatherings are banned under pandemic-era regulations.
It's a move that says as much about Europe's political polarisation along urban and rural lines as it does about the four countries involved.
"We have to return to our roots. Our world has abandoned God and Christianity," Robert Bakiewicz, head of a group organising the march, told the crowd.
Marek Kuchcinski from the ruling PiS party said he would resign after it was revealed that he used government aircraft for private trips by family members.
Poland is marking the 75th anniversary of the Warsaw Uprising during World War II.
A fire broke out on the upper floors of an under-construction building in the Polish capital Warsaw on Friday night.
On tonight's full episode of Raw Politics, panellists will be discussing the Venezuelan leadership lashing out at EU member states, the Spanish Prime Minister suffering a budget defeat, and Pompeo in Warsaw.
Scheduled to open in 2027, the new airport is hoped to become a regional hub and one of the largest international transfer airports in Europe.
How is the Polish capital establishing itself as a hub in which to live and invest?
Polish football fans unveiled a gigantic and provocative banner to mark a key date for the country in World War II.
Supporters of Legia Warsaw
Prince William and his family are in Poland and Germany to visit World War Two memorials and meet with locals
In major cities across Poland protesters condemn judicial changes which they say will kill judges' independence
Opposition protesters gather near the parliament in Warsaw to protest against the planned judiciary reforms announced by the ruling Law and Justice