Both sides were keen to put on a demonstration of strength amid a bitter political conflict that has divided Poland and attracted international criticism.
Protesters at the anti-government march, staged by the Committee for the Defence of Democracy (KOD) and most opposition parties, demonstrated against what they claim is the violation of democratic and European values by Poland's ruling party.
The march was the latest in a string of protests against reforms to the constitutional tribunal, public media, civil service and surveillance laws by the conservative Law and Justice party, which came to power in a landslide October election win.
Police said 45,000 anti-government demonstrators took to the streets, while Warsaw City Hall gave a vastly different estimate, putting the figure at 240,000.
The march, under the slogan “We are and will remain in Europe”, was held ahead of the EU's 9 May Europe Day and organised jointly by KOD and the opposition Civic Platform, Nowoczesna and Polish People's Party.
The counter-protest, staged by nationalists, conservatives and religious organisations, was held under the slogan “Poland Have Courage.”
It urged Law and Justice not to be cowed by what government supporters describe as cliques who cannot come to terms with losing the privileges they enjoyed under the previous centrist Civic Platform (PO) administration.
The counter-demonstration was attended by 4,500 people, according to police, while Warsaw City Hall put the figure at 2,500.
Counter-demo by nationalists in Warsaw. Photo: PAP/Bartłomiej Zborowski
Grzegorz Schetyna, head of the opposition Civic Platform party, told crowds: “We won’t allow a nightmare of authoritarian rule. We won’t allow the violation of democracy, the violation of the rule of law, violation of the constitution.”
Protesters carried blue EU flags and the red-and-white Polish national colours, and brandished anti-government slogans.
‘Dictates of Brussels’
Law and Justice leader Jarosław Kaczyński rejected claims that his party was opposed to the EU, saying: “We want to be members of the European Union because we want to have an impact on the fate of Europe.”
But Robert Winnicki, an MP and head of the National Movement (Ruch Narodowy), said the counter-march aimed to voice opposition to KOD, the "dictates of Brussels" and any moves to accept refugees in Poland.
He said a "leftist-liberal gangrene is destroying Europe. It’s a multicultural cancer."
Winnicki added: "The EU tries to limit Poland's sovereignty and interfere with what's happening in Poland. There are forces in Poland whom we call collaborators, who collaborate with Brussels."
The European Commission in January launched an inquiry into whether Poland is upholding the principle of the rule of law and whether controversial legislation pushed through by the Law and Justice government violates EU standards.
Law and Justice supporters have accused Polish opposition politicians of inciting Brussels to interfere in Poland's domestic affairs.
Speaking to internet users on Saturday, Kaczyński said the protests in Warsaw "were not a great worry" and insisted: “In Poland there is not the slightest danger to democracy, to civic freedoms and human rights.”
Meanwhile, a Schuman Parade also took place in Warsaw on Saturday under the slogan “Europe is here!”
Named after one of the founding fathers of the European Union, the parade was billed as non-political and aimed to promote the idea of European integration and civil society. (pk)
Source: PAP/Polish Radio/TVP/TVN