Serbian opposition leader Tomislav Nikolic, 59, who is refusing food or liquids, is lying on a sofa in the Serbian Progressive Party (SNS) offices in the parliament and intends to continue the protest until early elections are called, a statement from his nationalist party said.

"The SNS urges (President) Boris Tadic and his Democratic Party to call early elections, since these are not ordinary elections but a vote for the salvation of Serbia," it said.

"The SNS warns the regime that it bears entire responsibility for all political events that will shake Serbia in the coming days, weeks and months if it turns a deaf ear to citizens represented today by Tomislav Nikolic," it added.

Nikolic announced his decision during a Saturday protest staged by the SNS outside parliament that drew more than 50,000 people, ending without incident.

The opposition is pushing for elections on December 18, while the government insists that a vote should not be held until after a European Union decision on Serbia's membership application expected by the end of the year.

They argue that an election campaign in the autumn could hamper the EU accession process.

The SNS is tapping growing public discontent as Serbia struggles with rising prices, inflation and high unemployment.

Tadic's ruling party has slammed Nikolic for using a hunger strike to achieve his political goals.