Turkey's landmark election headed to a likely runoff on Sunday following a stormy night in which President Recep Tayyip Erdogan's secular rivals have contested the ballot count.

Erdogan sounded triumphant as he emerged before a sea of supporters shortly after midnight to proclaim himself ready to lead the nation for another five years, the New Arab reported.

Almost complete results from Turkey's most important election of its post-Ottoman era showed Erdogan -- in power since 2003 and undefeated in more than a dozen national votes -- falling just short of the 50-percent threshold needed to win.

"I wholeheartedly believe that we will continue to serve our people in the coming five years," the 69-year-old leader said to huge cheers.

The Anadolu state news agency showed the 69-year-old conservative leader on 49.3 percent.

Opposition leader Kemal Kilicdaroglu was trailing with 45.0 percent -- a disappointing outcome after late pre-election polls had shown him in the lead.

Turkey's first presidential runoff in the mostly Muslim but officially secular state's 100-year history is planned for May 28.

Kilicdaroglu's camp had initially contested the vote count and claimed to be ahead.

But the 74-year-old looked slightly despondent as he faced reporters early Monday and admitted that a runoff seemed inevitable.

"If our nation says second round, we will absolutely win in the second round," he said.

"The will for change in the society is higher than 50 percent."

But the secular opposition camp spearheaded by Kilicdaroglu cried foul.

"We are leading," the 74-year-old tweeted.

Leading opposition figures said the government was purposely slowing down the count in districts where Kilicdaroglu was enjoying strong support.

"They are contesting the count emerging from ballot boxes where we are massively ahead," Istanbul's opposition mayor Ekrem Imamoglu told reporters.

Imamoglu said the opposition's internal vote count showed Kilicdaroglu picking up 49 percent of the vote and Erdogan just 45.

But neither the state media count nor the one presented by the opposition avoids the possibility of Turkey holding another presidential vote in two weeks.