There were around 400 anti-government protesters in front of the Parliament building in Sofia by 7pm on Tuesday.
According to reports of the Interior Ministry a total of 12 people were arrested during Tuesday's rally over hooliganism and resisting police orders.
At around 8pm, the protesters tore down the metal railings, seeking to get as close to the building as possible, while riot police was pushing them back.
The building was only guarded by a police cordon for a while.
By 8.20 pm, the railings were back in place.
Earlier on Tuesday, an attempt to occupy the Parliament building resulted in clashes between police and protesters.
The protesters, many of whom were students participating in the sit-in at the "Sofia University St. Kliment Ohridski", tried to prevent the MPs from getting out of the building after a sitting.
Tuesday is the 152nd day of anti-government protests.
The rallies, which started in June, gathered steam over the past few weeks as students occupied the central building of the "Sofia University St. Kliment Ohridski", saying that they would not leave the site until the socialist-led cabinet resigned and the Parliament was dissolved.