Cyprus President Tassos Papadopoulos was trailing in the first round on Sunday of a presidential election seen as crucial to future efforts to reunify the island, according to latest results.
With more than half the votes counted, results showed that former foreign minister Ioannis Kasoulides and communist party leader Demetris Christofias were likely to go head-to-head in a runoff next Sunday.
Kasoulides, who is supported by the right-wing, led with 33.6 per cent, followed closely by parliament speaker Christofias with 33.14 and with 31.82 for the nationalist incumbent, according to results from 55.9 per cent of the vote shown on state television.
Official results were expected by 1830 GMT.
About half a million Greek Cypriots and about 400 Turkish Cypriots were registered to vote in the election, which the local press has billed as the most important in the history of Cyprus.
The results could prove a major upset for Papadopoulos, who was a narrow favourite in opinion polls and who has campaigned on a hardline stance on efforts to reunite the island after 34 years of partition.
His two main rivals had pledged to get peace talks back on track after they were effectively stalled following a Greek Cypriot rejection of a UN peace plan in 2004.
Chief returning officer Lazaros Savvides said turnout was about 90 percent. Voting is compulsory in Cyprus.
"In the end it will come down to party alliances and horse trading" in the week ahead of the runoff, when the candidate with 50 percent plus one vote will be declared the winner.
Cyprus has been split along ethnic lines since 1974 when Turkey invaded the northern third in response to an Athens-engineered coup aimed at uniting the east Mediterranean island with Greece.
"We need to find a Cyprus settlement that is a compromise between the best and worst that we can hope for," voter Maria Christou, 53, told AFP.
Warning that its patience was running thin, the United Nations -- which controls a buffer zone dividing southern Cyprus and the Turkish-occupied north -- has urged a resumption of peace talks.
International mediators hold Papadopoulos, 74, responsible for the failure of the UN blueprint, which led to a divided island joining the EU in 2004, although the Turkish Cypriots voted overwhelmingly in favour.
Turkish Cypriot leader Mehmet Talat's spokesman has charged that the presidential candidates planned policies aimed at hampering Turkey's EU bid to try to extract concessions on the Cyprus problem.
Last month the International Crisis Group think-tank said the rival leaders should hold talks as soon as possible after the election, warning that "if such efforts fail, the alternative is likely to be partition."
In campaigning, Papadopoulos had said his "no" vote meant he was the man to trust, suggesting his rivals would "sell out" the republic.
"We can expect more of the same from Papadopoulos. There will be no substantial progress on the Cyprus problem," said Hubert Faustmann, associate professor at the University of Nicosia.
"But from Christofias and Kasoulides we can expect considerable developments and a far more constructive approach from the Greek Cypriots."
Christofias, 61, has billed himself as the man to "build bridges" with the Turkish Cypriots, and Kasoulides, 59, too has said Cyprus needs to change tack by renewing contacts with the rival community and winning over EU member states.
Cyprus is at odds with the EU over Kosovo's declaration of independence, with Greek Cypriots fearing it could set a precedent for the self-declared Turkish Republic of Northern Cyprus which is recognised only by Ankara. (AFP)
Cyprus president trailing in key vote