Amnesty International on Thursday alleged police and justice authorities in Poland are suppressing anti-government protesters, a claim flatly rejected by the interior ministry.
"The Polish government is cracking down on peaceful protesters in a blatant attempt to dissuade further protests," AI said in a new report published on Thursday.
Titled "Poland: on the streets to defend human rights", it focuses on several demonstrations against the rightwing government's approach to justice issues, the rule of law and the women's rights organised earlier this year.
AI insists that protesters who hit the streets in July to demonstrate against judicial reforms by the Law and Justice (PiS) government "were exposed to abusive police practices that were unnecessary or disproportionate".
The international human rights group alleges that Polish "authorities use techniques such as surveillance, harassment and prosecution to disperse and prevent mass protests", insisting that these practices must stop.
Amnesty also urged Warsaw to respect freedom of assembly and expression.
Poland's interior ministry termed the allegations made by AI "unjustified" in a Thursday email to AFP.
Since taking office in 2015, the PiS government has provided heavy police protection for street demonstrations organised by groups on the right of the political spectrum, including the extreme right.
In August, police used force to remove protesters blocking a march by members of a far-right youth organisation in central Warsaw, insisting they were protecting a legal event.
Poland's foreign minister in August denied accusations his EU country was drifting towards authoritarianism amid a string of government reforms that have triggered mass protests at home and warnings from the EU.