Tens of thousands of people took to the streets of Warsaw Thursday to protest reforms by the pro-EU Polish government as the country suffers post-election turmoil.
The administration, led by a former European Council president Donald Tusk, ousted the right-wing populists of the Law and Justice (PiS) party in October elections.
Since then the two camps have frequently clashed over rule of law issues.
The bitter conflict has been highlighted by the case of two prominent PiS ex-lawmakers who were arrested on Tuesday at the presidential palace in Warsaw.
The men had been seeking refuge there on an invitation from the conservative head of state Andrzej Duda, allied with PiS, who announced he would pardon the pair as he considered them "political prisoners".
Mariusz Kaminski and Maciej Wasik were convicted in December and sentenced to two years in prison following a long legal dispute dating back to 2007.
Also last month, the new authorities in Warsaw sacked the management of all public broadcasters, which they argued had been used as a mouthpiece of the previous populist-nationalist government.
At the populists rally outside the parliament building in central Warsaw on Thursday, PiS politicians protested against both the media revamp and the high-profile arrests case.
"Free Poland is at stake here," PiS leader Jaroslaw Kaczynski told the crowd.
According to a city spokeswoman, around 35,000 people gathered at the protest, with the organisers estimating that nearly 200,000 attended.
One of the participants Jerzy Paluch, an 80-year-old retired army officer, called the current Polish administration "a mortal threat".
Speaking to an AFP reporter, he said he joined the rally to protest "the destruction of Poland as a state and of the Polish nation".
"We call for free media, as they are now being destroyed," Kaczynski, seen as Poland's de facto ruler during the PiS time in power, said at the rally.
He was joined onstage by former prime minister Mateusz Morawiecki who called on party supporters to "defend Poland".
"We were supposed to see a return to the rule of law but what we see is lawlessness," Morawiecki said.
The protest started shortly after the conservative Polish president announced he would pardon Kaminski and Wasik.
"This is extraordinary... we stand by your side," Morawiecki said referring to the arrest of the two men, currently still in detention, as their wives also joined the protest.
Two men had earlier announced a hunger strike while in jail.
Their case has gripped Poland and served as an example of the implications of the judiciary overhaul by the PiS, criticised by Brussels and the then pro-EU opposition.
Both men have denied the charges against them and have evoked a pardon that Duda granted them in 2015. That pardon, however, was later annulled by Poland's Supreme Court.
Legal experts at the time pointed out that the president could not pardon someone who had not yet been definitively convicted.
