Polish opposition leader Donald Tusk led a march in the capital, Warsaw, on Sunday to mobilize supporters ahead of the upcoming parliamentary elections.

Hundreds of thousands of people were bussed from across the country to take part in what has been dubbed the "March of a Million Hearts." 

Warsaw city authorities said about a million people attended in the capital's biggest rally on record, though other sources cited significantly lower numbers.

"When I see these hundreds of thousands of smiling faces, I have a good feeling that the breakthrough moment in the history of our homeland is coming," Tusk told supporters at the rally two weeks ahead October 15 general elections.

"Nothing can stop this force," said Tusk on Sunday. "Let no one in the ranks of power up there have any illusions. This change is inevitable."

Why is the opposition marching?

The opposition aims to unseat the nationalist Law and Justice (PiS) party, which Tusk has warned could try to take Poland out of the European Union. Tusk, formerly the country's prime minister, served as European Council president before returning to Polish politics.

"I want to be free, be in the EU, I want to have a say, I want to have free courts," Hanna Chaciewicz, a 59-year-old dentist from Otwock, told the Reuters news agency at the march.

The PiS, in power since 2015, denies it would aim to end the country's EU membership. The ruling party has nevertheless clashed several times with Brussels on various issues.

The ruling party is still ahead in the polls, with an IBRiS poll saying it stands at 35%. Meanwhile, the Civic Coalition opposition alliance stands at 27%, but Tusk has stressed that the party could still secure the coming vote.

The PiS also planned rival marches on Sunday in the southern city of Katowice.

js,rmt/lo (AFP, AP, Reuters)