Protesters rallied outside the presidential palace and the parliament building in Warsaw for a second day on Saturday over a government plan to restrict journalists' access to politicians in parliament.

The protests came amid rising political tensions over the ruling conservative Law and Justice party's new policies under chairman Jaroslaw Kaczynski and followed a large spontaneous demonstration on Friday outside parliament.

Mr Tusk, Poland's former prime minister, invoked the word "dictatorship" and reminded his audience of protests in Poland under communism that ended in bloodshed.

"I appeal to those who hold real power in our country to respect the people, the principles and values of the constitution, the standing procedures and good practices," Mr Tusk said in Wroclaw, south-west Poland, where he was attending a cultural event.

He warned that whoever was undermining the "European model of democracy" in Poland was "exposing us all to strategic risks".

A few hours later, prime minister Beata Szydlo said in a nationwide televised address that the opposition was guided by a sense of "helplessness and frustration" over having lost power and was hurting Poland's interest with its actions.

"Noise, perturbation, destabilisation have, alas, become the tools of the opposition parties," Ms Szydlo said, appealing for dialogue, responsibility and calm.

The crowd of a few thousand in Warsaw chanted "Freedom! Equality! Democracy!" and waved Polish and European Union flags, a reflection of the pro-European views of many liberal, urban Poles who oppose the ruling party.

"This conflict is entering a new, more aggressive phase," said Szymon Roginski, a photographer who joined the protest with his two young sons.

"Every day we hear news that makes us understand that we are further and further away from democracy. People have had enough."

President Andrzej Duda, who is allied with the ruling party, expressed deep concern and declared a readiness to mediate in the dispute.

The ruling party, which has increased welfare spending, still remains popular with many Poles, particularly those outside of the cities and on modest incomes.

Some protesters held up copies of the constitution, to show they believe it was not being observed by the ruling party.

They also chanted "Solidarity!", reflecting how many link today's protests to the anti-communist opposition of the past.

Ryszard Petru, head of the Modern opposition party, told the crowd in Warsaw that Poles would not accept the "dictators" who are trying to restrict the access of journalists to parliament. He even suggested an early election.

In Poland's biggest parliamentary crisis in years, opposition politicians protested against the government media plan on Friday, blocking a vote on the budget.

Governing party members then voted in another hall, but the opposition says the vote was flawed and illegal.

Opposition politicians are now demanding a repeat vote on Tuesday.

The senate speaker was to meet with media representatives to discuss the new rules for reporters.