WARSAW (Reuters) -Hundreds of thousands of protesters gathered in Warsaw on Sunday, the 34th anniversary of Poland's first postwar democratic election, for a march the liberal opposition has billed as a test of its ability to end nearly eight years of nationalist rule later this year.
Crowds stretching for at least a mile marched with banners reading "Free, European Poland", "European Union yes, PiS no", referring to the governing Law and Justice (PiS) party.
Some held masks of ruling party leader Jaroslaw Kaczynski that had the word "shame" written on them. Half a million people were marching, according to organizers. Police and city officials did not give an estimate. Thousands also marched in other Polish cities and towns.
"I took part in many marches, but I've never seen a protest of this size with such energy, I feel this is a breakthrough like June 4, 1989 was," Jacek Gwozdz, 51, an IT specialist from Nowy Sacz, said in Warsaw.
Opinion polls show an election due after the summer will be closely fought, with Russia's war in neighbouring Ukraine giving a boost to the Law and Justice (PiS) government which has emerged as a leading voice against the Kremlin in Europe.
The opposition has struggled to galvanise support despite widespread criticism at home and abroad of the PiS, which has been accused of eroding the rule of law, turning state media into a government mouthpiece and endorsing homophobia.
Prime Minister Mateusz Morawiecki's government denies subverting any democratic norms and says its aim is to protect traditional Christian values against liberal pressures from the West and to make the economy more fair.
Donald Tusk, head of the Civic Platform grouping and a former European Union council chief, welcomed supporters saying that the voice of Poles could not be silenced.
"Democracy dies in silence but you've raised your voice for democracy today, silence is over, we will shout," he said in a speech at the end of the march.
"There's half a million people in the streets of Warsaw, it's an absolute record," he told the crowds filling Castle Square in the capital.
Tusk called for unity despite political differences in the opposition and promised victory in elections that will be held in October or November.
"Today, I'm vowing to win, to make those in power accountable, to mend injustice so that in the end people can be reconciled," he said.
In June 1989, a partially free vote handed victory to a government led by the Solidarity trade union and triggered a series of events culminating in the fall of the Berlin Wall that November.
On Sunday, hundreds of buses arrived in Warsaw to bring opposition supporters from across the country. Some said they were motivated by a row over legislation proposed by PiS to weed out undue Russian influence from the country.
The opposition sees the legislation as a government attempt to launch a witchhunt against political opponents.
In an unexpected turnaround, President Andrzej Duda, a PiS ally, said on Friday he would propose amendments to the law, which has also drawn criticism from lawyers, as well as the United States and the European Commission.
The EU's executive said the legislation could effectively ban individuals from holding public office without proper judicial review.
"It's beyond comprehension," said Andrzej Majewski, 48, from Slupca in western Poland who was in Warsaw to join Sunday's protest march.
(Reporting by Marek Strzelecki and Kuba Stezycki; Editing by Nick Macfie, Susan Fenton and Angus MacSwan)