Chanting democracy slogans, several thousand people rallied in Warsaw in demonstrations against controversial new court reforms they see as a threat to judicial independence.
Protesters waved EU and Polish flags and shouted "we will defend democracy" at an afternoon demonstration in front of the parliament, which this week passed legislation that critics say gives the ruling Law and Justice (PiS) party power over the courts.
Participants called PiS leader Jaroslaw Kaczynski a "dictator" and held up signs with slogans such as "duck off" in reference to the similarity of his last name to the Polish word for duck.
Police estimated the crowd at 4,500 people, while the city authorities said there were more than 10,000 protesters at the demonstration, organised by the KOD pro-democracy movement, which is critical of the governing conservatives' policies on courts as well as other areas such as media and education.
Later on Sunday, the Iustitia association of Polish judges held its own protest in front of the Supreme Court, where 17,000 people according to the city held up candles and called out in favour of "free courts".
"This whole set of (judicial) bills is a scandal," said Agnieszka Janczarska, a 39-year-old lawyer in Warsaw who attended both demonstrations.
"It's a destruction of the fundamental principles of a democratic state, namely the separation of powers," she told AFP.
The two main opposition leaders, Grzegorz Schetyna from the Civic Platform (PO) and Ryszard Petru from the Modern party, said at the afternoon rally that they would join forces to fight against the reforms.
Poles also rallied in other cities across Poland including Krakow, Szczecin and Wroclaw.
Earlier this week the parliament adopted a bill that gives the minister of justice the power to name the chief justices of the EU member's common courts.
Lawmakers also passed a second bill that states that from now on the parliament -- which is controlled by the conservative PiS party -- will choose the members of the National Council of the Judiciary (KRS), whose role is to protect the independence of courts.
"We're implementing good changes for Poles, for those who are waiting for a well-functioning system of justice," senate speaker Stanislaw Karczewski, a PiS member, told reporters.
The PiS also tabled a separate bill in parliament on Thursday that would subjugate the Supreme Court -- which supervises lower courts -- to executive power, in a move the opposition slammed as "the announcement of a coup".
Under the proposed bill, the current Supreme Court justices will be forced to retire, with the exception of those named by the justice minister, who would also be responsible for selecting candidates to succeed the retired judges.