Warsaw, Poland: Opposition groups have massed in demonstrations across Poland, enraged by the new government's efforts to exert its influence on the nation's media supervisors and top courts.

The protests, which were organised by the Committee for the Defence of Democracy, drew about 20,000 people in Warsaw on Saturday, while other gatherings were reported nationwide.

A demonstrator seals his mouth during a protest over media freedom at the Polish TVP News headquarters in Warsaw. Credit:AP

"If journalists cannot keep an eye on the powerful, then people will not know what the government is up to," committee leader Mateusz Kijowski said at a rally in the central Polish city of Lodz.

The conservative government, which took power in November, has angered many with the new measures. The changes give newly installed conservative judges a greater say on the nation's highest court and let the government install a political appointee to head public broadcasters.