Many of the protesters had camped overnight outside the parliament building in the capital, Tbilisi.

The crowd has swelled during the day, but has not yet matched the 50,000-strong crowd seen on Friday.

The protesters want an early election, accusing the president of leading a corrupt, authoritarian government.

The pro-Western Mr Saakashvili came to power in January 2004 following the peaceful "Rose revolution", which toppled President Eduard Shevardnadze.

The country is still struggling to recover from years of post-Soviet economic decay, instability and civil war.

The president remains popular among much of the population, reports the BBC's Matthew Collin in Tbilisi - but the opposition is also hoping to capitalise on discontent with widespread poverty.

"Saakashvili has said absolutely nothing. How can he stay silent when tens of thousands of people are on the streets? It shows he thinks nothing of us," 23-year-old Levan Kaprindashvili told AFP news agency.

'Political blackmail'

The country's previously weak and divided opposition parties formed a united front last month, and began a nationwide protest campaign against the Georgian leader.

The government has accused the opposition of using the protest as a form of blackmail.

Mr Saakashvili said on Thursday that Georgia was a failed state before he came to power but had now become a model of democratic development and economic reform.