Tens of thousands of Moldovans took to the streets on Sunday in the capital Chisinau calling for early elections as the country continues to be rocked by a $1 billion banking scandal.

The leftwing organisers of the demo said between 25,000 and 40,000 people turned out to show their anger over corruption in the former Soviet nation, which is one of the poorest in Europe.

Police did not provide a crowd estimate.

"If President Nicolae Timofti does not resign before the end of next week, we will intensify our protests," said Socialist Party president Igor Dodon.

"Early parliamentary elections must take place no later than the beginning of spring 2016," he said.

Protests in the country of 3.5 million have been triggered by an eye-popping scam that saw 1 billion euros ($1.1 billion) -- roughly 15 percent of Moldova's GDP -- mysteriously exit the country.

The scam, uncovered early this year, has been dubbed the "fraud of the century" and came as a devastating blow, triggering the devaluation of the national currency, the leu, and stoking inflation.

Renato Oussaty, the head of left-wing Our Party, said the protests aim to "free Moldova from oligarchs who have seized the country."

This demo comes on the heels of an anti-corruption protest led by the Dignity and Justice movement that organisers said drew 100,000 people on September 6, though police put the number at 30,000.

The demonstrators, who also set up a 300-tent encampment in the centre of the capital three weeks ago, accuse the country's leaders of paying lip service to Western integration, while using their positions of power to enrich themselves.

Among the demonstrators' demands are the resignation of Timofti, early parliamentary polls and the dismissal of top officials at the central bank and the prosecutor general's office.

Protesters on Sunday also called on the heads of the country's security services, national radio and TV channel to step down.

"We must first get rid of the leadership and then decide our direction: neither Moscow, nor Brussels nor Washington are going to fix our problems," Oussaty said.