Poles gathered in cities across the country to show support for the European Union after the nation’s constitutional court recently ruled that the Polish constitution overrides some EU laws.

Donald Tusk, the top opposition leader in Poland and a former EU leader, called for the protest, casting it as an effort to defend the country’s continued membership in the 27-nation EU.

“We have to save Poland, no-one will do it for us,” Mr Tusk said.

Broadcaster TVN24 showed crowds gathering in Warsaw, Krakow, Poznan and other cities with EU and Polish flags.

Thousands of people filled Castle Square in the historic centre of Warsaw, with people chanting “We are staying!” Some held signs with slogans including “We are Europeans”.

In Warsaw, whose mayor hails from Mr Tusk’s Civic Platform party, EU and Polish flags hung from lampposts and city buses ahead of the evening rally.

In Poland, critics of the right-wing nationalist government fear that the court ruling could lead to an eventual “Polexit”, or Poland being eventually forced to leave the EU over an impression that it is rejecting the bloc’s laws and values.

The government of Prime Minister Mateusz Morawiecki denies that it is seeking to leave the bloc, although top members of the ruling party have recently used language suggesting this might be their aim.

EU membership is extremely popular in Poland, having brought new freedom to travel and a dramatic economic transformation to the central European nation, which had endured decades of communist rule until 1989.

Speaking to the crowd in Warsaw, Mr Tusk warned that a “pseudo court … by order of the party’s leader, in violation of the constitution, decided to take Poland out of the EU”.

“We want an independent, law-abiding, democratic and fair Poland,” Mr Tusk said, before the crowd sang the national anthem.

The court ruling, which was issued on Thursday by a court loyal to the nationalist government, marks a dramatic challenge to the primacy of EU law.

In a legal decision requested by Poland’s prime minister, the tribunal held on Thursday that the Polish constitution has primacy over EU laws in some cases.

Mr Morawiecki asked for the review after the European Court of Justice ruled in March that Poland’s new regulations for appointing Supreme Court justices could violate EU law and ordered the right-wing government to suspend them.