Turkey's election rivals are both claiming to have the lead with counting under way in the poll.

Parties of both current President Recep Tayyip Erdogan and main opposition challenger Kemal Kilicdaroglu both say they have the edge, with news agencies in the country offering competing results.

Both sides dismissed the other's count, with no official result announced.

Mr Erdogan, 69, is seeking a third consecutive term as president but faces his toughest ever challenge.

Despite both sides claiming to have a lead, sources in both camps told the Reuters news agency that they may not clear the 50% threshold needed to win outright.

If no presidential candidate secures more than 50% of the vote, a run-off election will be held on 28 May.