Leading rights group Amnesty International warned Monday that freedom of assembly was at risk in Poland just as the EU was poised to launch hearings over fears that Warsaw was undermining judicial independence.
In its new report, Amnesty warned that "restrictive legislation combined with heavy-handed policing, surveillance, harassment and prosecution threaten to strangle the right to peaceful protest" in Poland.
"Peaceful protest is a right, but in Poland it is under serious threat," the organisation's Europe director Gauri van Gulik told reporters in Warsaw.
Tens of thousands of Poles have hit the streets since the rightwing Law and Justice (PiS) government came to power in 2015 to rally against its controversial judicial reforms and attempts to tighten Poland's already strict abortion laws, among other causes.
In one case last August, police used force to remove protesters peacefully blocking a march by members of a far-right youth organisation in central Warsaw, insisting they were protecting a legal event.
Amnesty remarked that "the authorities often give preferential treatment to pro-government and nationalist demonstrations over other types of assemblies".
It also found that "harassment or violence by far-right or nationalist groups (is) regularly tolerated when directed against counter-protesters".
"We have documented several cases of excessive use of force against protesters" by police, van Gulik told reporters, adding that protesters were also subject to a high rate of prosecution.
"This is really where Poland is quite a unique situation in Europe and really globally in some ways," van Gulik said, adding that "there were over 600 prosecutions of protesters last year alone.
"That criminalisation of protest has to end," she said.
Amnesty's Europe chief also said the group had "reason to believe that surveillance is used in a widespread and quite arbitrary way against protesters".
According to Amnesty, judges in Poland are also "experiencing political pressure" in connection with the PiS government's judicial reforms.
Warsaw insists the changes are needed to combat corruption and overhaul a judicial system still haunted by the communist era, but critics including the EU argue they undermine the division of powers and therefore threaten democracy and the rule of law.
"Those judges who have refused to bow to it (political pressure) in the wake of the reforms have already reported harassment, including disciplinary proceedings," the Amnesty report alleges.
The EU is expected to launch hearings on Tuesday focused on Poland's alleged violation of judicial independence.
Brussels in December triggered so-called article seven proceedings against Poland over "systemic threats" to the rule of law, which could eventually see Warsaw's EU voting rights suspended.