Protesters have blockaded the Polish parliament in Warsaw in support of opposition MPs unhappy about new rules restricting press reporting.
Police intervened to clear a path for government officials to leave by car after a late-night stand-off.
Poland's populist right-wing government wants to limit the number of reporters allowed to cover parliament.
The MPs' protest delayed a vote on the budget, which was held later, away from the main chamber.
The opposition accused the government of passing next year's budget unlawfully earlier on Friday evening by transferring the key vote to a smaller hall and excluding the press.
It was the first time since the restoration of democracy in 1989 that such a vote was held outside the main chamber of parliament.
Enough MPs were present for the budget vote to be valid, according to the leader of the governing Law and Justice (PiS) party, Jaroslaw Kaczysnki, and other party members.
The opposition has demanded a rerun of the vote in the main parliament chamber next week.
"There is no proof that a quorum of lawmakers was present. We suspect that people who were not allowed to vote took part," said leader of the opposition Nowoczesna party Ryszard Petru.
Michal Szczerba, a MP from the opposition Civic Platform party, tweeted early on Saturday: "For the first time I have seen armed police at the parliament building."
Mr Kaczynski earlier denounced the protest as "hooliganism".
"We will not allow ourselves to be terrorised,'' he said.
He left parliament with the PiS Prime Minister Beata Szydlo at about 03:00 (02:00 GMT).
Opposition MP Jerzy Meysztowicz told the TVN24 news channel that police used tear gas to clear a passage through protesters for their official vehicle.
Police spokesman Maruisz Mrozek, quoted by Reuters, denied use of tear gas but said physical force was required to remove protesters.
PiS has been accused of restricting press freedom since coming to power last year.
Next year only a few reporters will be allowed into parliament, with five selected TV stations permitted to make recordings of parliamentary sessions.
"This restriction, first of all, does not hit journalists, but the rights of citizens to be fully informed about what people elected by them to the parliament do," a statement compiled by the country's largest independent news organisations said on Friday.
The government argues that the measures are not restrictive and will stop MPs from being accosted by journalists inside the parliamentary building.
Opposition MPs began the protest inside parliament on Friday with one MP holding aloft a placard reading "free media".
He was told by Speaker Marek Kuchcinski, who is a PiS member, that he would no longer be allowed to attend parliamentary proceedings.
But other opposition MPs converged on the podium, in what is believed to be the first protest of its kind in the chamber for 10 years.