The rally, organised by the Civic Coalition Party, commemorated the 35th anniversary of Poland's first partially free 1989 election.
ADVERTISEMENTSupporters of Polish Prime Minister Donald Tusk gathered in Warsaw for a rally on Tuesday, a few days ahead of the European elections.
The supporters gathered in Warsaw's Castle Square carrying banners reading "We are citizens of the EU."
The date of the rally, 4 June, marks the anniversary of Poland's first partially free elections in 1989 when the country was still one of the Soviet Union's satellite states.
Addressing supporters, Tusk outlined the importance of the upcoming European elections for the future of Europe and the war between Russia and Ukraine.
"I, for one, am very worried about the outcome of these elections. I would personally very much like to be with Europe, and I can't imagine a different future," Tusk said.
"Listen, believe me. Over there in the Kremlin, for them (the Russian government), the possible political capture of Brussels would be more important than the capture of Kharkiv. This fight over who will rule in Poland, and now the fight over who will rule in Europe, is also a fight to prevent war from entering our borders," he added.
The rally hoped to mobilise supporters of Tusk's Citizens Coalition ahead of the European elections on 9 June.
Tusk's Civic Coalition is the largest group in Poland's generally pro-European coalition government.
Tusk, a former European Council president, took over from Poland's previous right-wing nationalist Law and Justice or PiS party, which was critical of the European Union.
Tusk hopes his party will win the most European Parliament seats assigned to Poland in the election, which would boost the Civic Coalition as a dominant force in Polish politics. In turn, PiS has accused Tusk of being subservient to its neighbouring country, Germany, and to Brussels more generally.