Türkiye appears headed for a run-off presidential election after neither Recep Tayyip Erdoğan nor opposition rival Kemal Kılıçdaroğlu cleared the threshold to win outright on Sunday, in a poll seen as a verdict on Mr Erdoğan's 20-year rule and increasingly authoritarian path.

With almost 92 per cent of ballot boxes counted, the head of Türkiye's High Election Board said Mr Erdoğan was leading with 49.49 per cent, to 44.79 per cent for Mr Kılıçdaroğlu.

Earlier, both sides claimed to be ahead and contested the figures, warning against any premature conclusions in a deeply polarised country.

In a fiery speech to an exuberant crowd outside his party's headquarters in Ankara, Mr Erdoğan said he was 2.6 million votes ahead of his rival, but he stopped short of declaring outright victory.

"We don't yet know if the elections ended in the first round," he said.

Mr Erdoğan said he expected to win without a run-off, but "if our nation has chosen for a second round, that is also welcome".

Mr Kılıçdaroğlu said he will accept the people's decision for a second round, adding Mr Erdoğan had not obtained the result he wanted.

Speaking alongside leaders of the other parties in his alliance, Mr Kılıçdaroğlu said he will win in the run-off against Mr Erdoğan.

Opinion polls before the election had pointed to a very tight race but gave Mr Kılıçdaroğlu, who heads a six-party alliance, a slight lead.

Mr Erdoğan said he expected to win without a run-off, but "if our nation has chosen for a second round, that is also welcome".

Mr Kılıçdaroğlu said he will accept the people's decision for a second round, adding Mr Erdoğan had not obtained the result he wanted.

Speaking alongside leaders of the other parties in his alliance, Mr Kılıçdaroğlu said he will win in the run-off against Mr Erdoğan.

Opinion polls before the election had pointed to a very tight race but gave Mr Kılıçdaroğlu, who heads a six-party alliance, a slight lead.

A majority of ballots from the 3.4 million eligible voters living abroad still needed to be tallied, according to the board, and a run-off election was not assured.

The vote is one of the most consequential elections in the country's 100-year history, a contest that could end Mr Erdoğan's imperious 20-year rule and reverberate well beyond Türkiye's borders.

READ MORE: Türkiye could face run-off election after tight race between Recep Tayyip Erdoğan​​​​​​​ and opposition leader Kemal Kılıçdaroğlu