Preliminary results show Erdogan losing majority in Turkey's fiercely fought elections

Neither Turkey's President Recep Tayyip Erdogan nor his main rival looked to have secured the 50% of votes to win the elections, preliminary election results showed, raising the prospects of a runoff vote.

State-run Anadolu news agency reported projections based on 90.54% of the votes counted, showing Erdogan having 49.86% of votes, compared to 44.38% for the main opposition candidate, Kemal Kilicdaroglu.

The third candidate, Sinan Ogan, received 5.30% of votes, according to Anadolu, raising the possibility he could be a kingmaker in a runoff. He tweeted that a second vote is "quite possible," and that "Turkish nationalists and Ataturkists are in a key position for this election."

Sunday's race poses the biggest challenge yet to Turkey's strongman leader. He faces economic headwinds and criticism that the impact of the devastating February 6 earthquake was made worse by lax building controls and a shambolic rescue effort.

Ballots of the 64 million eligible to vote were still being counted six hours after polling stations closed across the country.

For the first time, Turkey's factious opposition has coalesced around a single candidate, Kilicdaroglu, who represents an election coalition of six opposition parties.

Earlier on Sunday, Ankara Mayor Mansur Yavas, who is the vice-presidential candidate for the main opposition Nation Alliance bloc, contested Anadolu's results, saying the agency is unreliable. He added that the opposition's data showed Kilicdaroglu as being ahead of Erdogan.