Istanbul - Incumbent Turkish President Recep Tayyip Erdogan has declared victory in Sunday's runoff election.

He spoke to supporters after preliminary results gave him 53% of the vote, compared with 47% for his challenger Kemal Kilicdaroglu.

"I thank each member of our nation for entrusting me with the responsibility to govern this country once again for the upcoming five years," said Erdogan, who had been seeking a third decade in power.

He was seen as the front-runner heading into Sunday's vote after narrowly missing victory in the first round.

Both Erdogan and Kilicdaroglu said at last-minute rallies Saturday that turnout would be key to the outcome of the presidential poll.

Supporters of Turkish President Recep Tayyip Erdogan watch the results outside AK Party offices in Istanbul, May 28, 2023.

Bugra, a voter who only wanted to be identified by his first name, said democracy itself is on the ballot.

"People's rule, the republic, these are the values we have come here to defend. For 20 years, this government has only been trying to lead us to a legitimate monarchy, trying to make the parliament dysfunctional," he said.

Critics accused Erdogan of undermining democracy, locking up critics, and centralizing power. Challenger Kilicdaroglu pledged to return to Turkey to parliamentary democracy and releasing prominent political prisoners.

But Erdogan played the nationalist card, accusing his challenger of being soft on terrorism, and insisting that the country needs strong leadership to stand up to Turkey's Western allies and navigate the dangerous challenges posed by a neighborhood that includes Syria and Ukraine.

It is a stance that resonated with another voter, Yunus Koz.

"It is very important. I am a Muslim, I am Turkish, I love this homeland very much, and I want my homeland to remain in the hands of Tayyip Erdogan. The other side [Kilicdaroglu], wants it to be in the hands of imperialist powers," Koz said.

Erdogan was the top vote getter in the first round but Kilicdaroglu remained competitive with his pivot toward hardline nationalist policies, including calling for the return of millions of Syrian refugees.

Moreover, with Erdogan's voters turning out in larger numbers than Kilicdaroglu's in their respective strongholds in the first round, increasing the voter turnout of his base is now seen as Kilicdaroglu's best chance of winning.