The Greek government has secured enough votes to pass deeply unpopular austerity measures essential to unlocking further aid from foreign lenders.

The fragile three-party coalition managed to secure at least 151 votes.

These votes were needed to win approval for the package of spending cuts, tax hikes and labour reforms despite the junior-ruling Democratic Left party's refusal to back it.

Outside parliament buildings in Athens, violence erupted as a handful of protesters tried to break through a barricade to enter parliament.

The parliamentary session was briefly interrupted when parliament workers went on strike and opposition lawmakers walked out of the chamber in protest.

Protesters hurled petrol bombs and police responded with teargas, stun grenades and water cannons.

A sea of Greeks braved a steady downpour holding flags and banners saying "It's them or us!" and "End this disaster!" stood before riot police guarding parliament.

In all, nearly 100,000 protesters - some chanting "Fight! They're drinking our blood" - packed the square and side streets in one of the largest rallies seen in months, police said.

Protesters held aloft Italian, Portuguese and Spanish flags in solidarity with other southern European nations enduring austerity.

Public transport was halted, schools, banks and government offices were shut and rubbish was piling up on streets on the second day of a two-day nationwide strike, called to protest against the vote.

Greeks have also expressed outrage at the lacklustre approach consecutive governments have taken towards catching tax cheats.

Many say officials have dragged their feet on investigations to protect a wealthy elite.

Following the publishing last month of the so-called "Lagarde List" of more than 2,000 wealthy Greeks with Swiss bank accounts, the Swiss government said it was looking to clinch a swift deal with Athens on taxing secret holdings.

The austerity measures are accompanied by steps to make it easier for businesses to hire and fire workers.

The measures include reductions to severance pay and the warning time employers must give workers before they let them go.

The junior ruling Democratic Left party refused to support these, saying they have no bearing on Greece's fiscal targets under the bailout plan.