Anti-riot police broke up a protesters' blockade of Bulgaria's parliament and escorted out over 100 ministers, politicians and journalists who had been trapped inside for more more than eight hours.

Policeman with shields pushed away the anti-government protesters on Wednesday and formed a tight cordon to get the trapped out of the state building in Sofia, hours after demonstrations turned violent.

Shouting "mafia" and "resign", opponents of the Socialist-led government on Tuesday threw plastic bottles and other objects at a heavily-guarded bus that had earlier tried to get deputies out of the parliament where they had been discussing budget measures.

Stones flew, breaking several windows on the bus, as police in anti-riot gear tried to push the protesters back to make way for the vehicle. Demonstrators shouted "Murderers!" as dozens of police in riot gear pushed and clubbed them to clear a path for the bus. After an hour, the vehicle had to return to the building. The people hurt included some with head injuries.

A total of 109 people - including three ministers and 30 other politicians, journalists and parliament staff - were trapped, according to national television.

Seven protesters and two police officers were treated in hospital for head wounds, national radio reported. .

The Socialist-backed government took office after early elections in May, following the resignation of the previous cabinet amid anti-austerity protests. The government commands only 120 seats in the 240-seat Parliament and has to rely on the tacit support of a nationalist party.

Anger and protests

The appointment of controversial media mogul Delyan Peevski as head of the national security agency has sparked public anger and daily protests since June 14. The appointment was immediately revoked but demonstrators insist the government is corrupt and must resign.

The government's withdrawal of the appointment failed to quell public discontent in the European Union's poorest country, which also is one of the bloc's most corrupt.

President Rosen Plevneliev appealed to protesters and police to keep the demonstrations peaceful as they had been for the past 40 days, and to avoid provocation.

"I appeal to the protesters to keep the protest the way it was and the way it impressed all of Europe - peaceful, civilised and aimed at achieving the values of a democratic society," Plevneliev said in a statement.

The opposition centre-right GERB party urged Prime Minister Plamen Oresharski to resign immediately and called on the president to hold an emergency meeting of the national security council.

Earlier on Tuesday, the European Union's justice commissioner Viviane Reding said she sympathised with the protesters who rallied against corruption, and urged the government to reform its judicial system.