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WARSAW (Reuters) - Several thousand people demonstrated in Warsaw on Saturday against Poland’s conservative, eurosceptic ruling party in an attempt by the opposition to build momentum ahead of next year’s municipal elections.

The crowd, variously estimated at between 10,000 and 20,000, fell short of the mass protests that took place after the Law and Justice (PiS) party won power in late 2015 and swiftly moved to implement reforms, including an overhaul of the country’s top court.

But the gathering under the “Freedom March” slogan was still the largest the opposition, headed by the centrist Civic Platform (PO) party, has been able to muster in recent months.

“We are for a democratic Poland, for a European Poland, for Poland that is proud, that seeks friends and partners, not enemies in Europe as it is today,” PO leader Grzegorz Schetyna, told protesters waving Polish and European Union flags.

The PiS government has been under fire from the European Union over changes to the constitutional court, which Brussels says could undermine democratic checks and balances.

It has also been criticised for tightening its control of public media. The European Commision is to present its report on the situation in Poland at a meeting on May 16.

Jaroslaw Kaczynski, the head of PiS, said that freedom was not at risk in Poland in comments aimed at the protesters.

“Today we do have freedom and by taking part in this march and claiming that today freedom is at stake, as a matter of fact, you are marching (in the name of) the opposite,” Kaczynski said during a visit to a shipyard in the Baltic city of Szczecin.

The two parties are vying for electorate support in Poland’s municipal elections, scheduled for 2018, with recent polls showing the opposition ahead of PiS for the first time since 2015.