WARSAW, Poland (AP) — A leading press freedom group is calling on Polish authorities to “end their harassment and attempts to intimidate independent journalists,” after a string of incidents that have raised concerns about media freedom.

Perceived attacks on media freedom have also triggered a strong rebuke from the U.S. ambassador in recent weeks, sparking tensions between the United States and the national-conservative government of Law and Justice, led by Jaroslaw Kaczynski.

Paris-based Reporters Without Borders on Friday cited a number of examples in which authorities have used their powers to summon journalists to prosecutors. It also noted that the head of the National Bank of Poland and a senator with the ruling party recently threatened to sue five journalists if they did not remove seven allegedly defamatory articles from the newspaper’s website.