An estimated 60,000 people protested outside parliament in central Athens on Sunday night against cuts and tax rises.
The BBC reports it was the biggest demonstration in 12 consecutive days of protests.
Prime minister George Papandreou is trying to boost support for an updated austerity plan in the Pasok party before presenting it to parliament.
EU and IMF officials say the next tranche of their 110 billion euro ($US159 billion) bail-out package for Greece will be paid, most likely in July.
The BBC reports the protesters call themselves ''Indignant Citizens'' - a name similar to that used in Madrid where their counterparts are known as ''los indignados'' (the indignant).
The organisers said they were independent of the trade unions, which have also staged anti-austerity protests in recent months.
