Polish President Andrzej Duda scrambled Monday to defuse a political crisis as opposition lawmakers occupied parliament for a fourth day to protest at an "

Thousands of demonstrators have taken to the streets since Friday in Warsaw and other parts of the country in the latest popular action against moves deemed anti-democratic by the governing rightwing Law and Justice party (PiS) since it took office after October 2015 elections.

Dozens of opposition MPs seized parliament's main chamber and protesters blocked the exits to the building on Friday in a defiant show of anger against the government.

Thousands of protesters -- grouped in a popular movement called the Committee for the Defence of Democracy -- rallied outside parliament in support of the opposition MPs until late Sunday.

A smaller pro-government rally took place outside the presidential palace.

In Krakow on Sunday, police removed protesters who laid on the ground to block the car of influential PiS leader Jaroslaw Kaczynski, who was visiting the grave of his twin brother, former president Lech Kaczynski who died in a plane crash in Russia in 2010.

Duda, who has appealed for calm, launched mediation talks with opposition leaders on Sunday.

The president scheduled further meetings on Monday with Kaczynski and parliament speaker Marek Kuchcinski.

Kaczynski has indicated that his party is ready to discuss the new rules with journalists, and the official news agency PAP quoted an unnamed member of the government as saying he is "not happy" with the measures.

'Illegal' budget vote

The opposition lawmakers also called for re-run of a parliament vote on next year's budget, which they claim was approved illegally when it was held in another area of parliament after the opposition takeover of the main chamber.

Since taking office, the PiS has come under fire over a string of controversial measures including tightening its control over the media and pushing through changes to the constitutional court which led to a standoff with the European Union.

Monday marks that last day in office of the outgoing president of the constitutional court, Andrzej Rzeplinski, a symbol of resistance to the government.

The question of his successor has become another bone of contention between the court and the PiS-dominated parliament.

The latest opposition outcry was triggered by PiS plans to grant access to the parliament's press gallery to only two journalists for every media outlet, and ban them from shooting still pictures or video.

The moves prevent the media from recording images of lawmakers when they break the rules, for example by voting for an absent colleague.

The PiS has defended the measure, saying it was seeking to ensure a comfortable working environment for both lawmakers and journalists.

Duda on Monday also approved a law lowering the retirement age to 65 for men and to 60 for women.

The former centrist government had raised the limit for both sexes to 67.

The new law -- which the opposition says would harm the economy -- was among the promises made by the PiS during its electoral campaign.