Poland's government backed the disputed publication of pictures of some protesters who demonstrated outside parliament last month, saying on Wednesday they should face prosecution.
Warsaw police published 21 photos of the unidentified people on their website, saying they might be connected to acts amounting to a "violation of the legal order" during the protest over a now-dropped plan to limit media access to parliament.
The Helsinki Foundation for Human Rights, however, said publishing the images lacked any legal basis and would have a "chilling effect" on all those who wanted to protest in Poland in the future. None of those pictured have been charged.
The government of the Law and Justice (PiS) party, which came to power in 2015, has already been accused by the European Union executive of passing legislation that is at odds with the EU's democratic values and weakening judicial independence. Interior Minister Mariusz Blaszczak said police had identified 80 people who attempted to "ignite a riot" on December 16 around parliament.
"The people whose photos have been published - we are asking them to come forward ... so they are held responsible for breaking the law," Blaszczak told journalists.
The police are asking anybody recognizing the people to provide information. State television also aired some of the images of the protesters on Wednesday.
"There is no legal basis for publishing these images. These people are not suspects," said Piotr Kladoczny of the Helsinki Foundation for Human Rights, which is prominent in Eastern Europe. "This will have a chilling effect on people who want to demonstrate."
Once considered a model of a transition from post-Communism to democracy, Poland has been criticized over the past year by human rights groups for action they say poses risks to the rule of law, freedom of the media and civil rights.
"We are dealing here with abuse of power [by the police]," former interior minister and lawyer Ryszard Kalisz told broadcaster TVN24. "The whole legal society is appalled."
During the protest, police forcibly broke up an hours-long blockade of the parliament by demonstrators who backed a sit-in inside the plenary hall by opposition lawmakers.
Television images showed back then some protesters shouting at ruling party lawmakers as they walked out of parliament.
A spokesman for the Warsaw prosecutor's office, Michal Dziekanski, said police had a right to publish images of people whose identity had not been determined.
"It is not the political aspect that is important for us, but stories connected with using violence against other people," Dziekanski said.
He said that one person whose image was published had contacted the police and been charged with verbal abuse, which is a crime in Poland.