Five people were arrested in clashes on Tuesday between police and Bulgarian students who had cordoned off parliament in the capital Sofia as part of an anti-government protest, police said.
Skirmishes erupted and at least one person was injured as officers tried to push back the students, who had formed a tight human chain along the metal fence encircling the building and vowed to prevent lawmakers from leaving.
The protest came a day after students padlocked Sofia University -- opposite parliament -- demanding the resignation of Prime Minister Plamen Oresharski's embattled Socialist-backed government.
"The university occupation is not ending. It is changing into an active blockade of parliament," the students announced on their Facebook page Tuesday, urging supporters to join them.
Several hundred people answered the call to form the human chain.
The protesters outside the building booed and shouted: "You are a disgrace. Resignation and jail!" and "We will be here every day until we win."
Deputies however had already entered the building and parliament business went on as usual.
MPs were debating next year's budget, which is due to be put to a vote later this week.
Whether they would be able to leave after the end of their session was unclear.
The European Union's poorest member state has been rocked by anti-government protests since February, when public anger forced the resignation of the previous conservative cabinet.
Ongoing protests against corruption and politicians' links to the oligarchy brought up to 20,000 people into the streets over the summer, but the demos had subsided in recent months.
The student rallies could now reignite mass anti-government unrest, analysts warn.
A previous blockade of parliament in July trapped over 100 lawmakers, journalists and administrative staff in the building for over eight hours, ending with skirmishes between some 2000 protesters and police. At least eight protesters and two policemen were injured.