The centre-left mayor of Slovenia's capital Ljubljana was headed for victory in a parliamentary election on Sunday, early results showed, making the outgoing Social Democrats the latest casualties of the euro zone economic crisis.

The defeat for Prime Minister Borut Pahor was expected, but the victory for Ljubljana Mayor Zoran Jankovic, if confirmed, would mark an upset after weeks of opinion polls predicting a comfortable win for centre-right ex-prime minister Janez Jansa.

With nearly a third of votes counted, Jankovic's party was leading with 29.5 percent of the vote over Jansa's party with 25.9 percent and Pahor's party with less than 10.3 percent.

Jankovic will have to seek coalition partners, and Pahor said his party was ready to talk.

We are open for dialogue, the outgoing prime minister told Pop Television. We have to think of the future of this country.

An Alpine state of 2 million people, EU and euro zone member Slovenia was once a model of successful post-communist transition but is now facing renewed economic contraction, rising unemployment and the threat of a credit rating downgrade.

Pahor's government lost its majority in May amid internal policy squabbles and was ousted by parliament in September.