The dreams of Turkey's opposition gave way to crushing disappointment on Sunday as President Recep Tayyip Erdogan narrowly won a historic runoff election to extend his two-decade rule to 2028.

Opposition leader Kemal Kilicdaroglu entered the country's first ever runoff as the clear underdog after Erdogan came within a whisker of winning outright in the first round on May 14.

Yet his supporters harboured hopes that the secular CHP party leader could oust the Islamic-rooted conservative president against all the odds.

After all, Kilicdaroglu picked up more votes against Erdogan than any other opposition leader, denying him a first-round victory for the first time in his dominant rule.

"A miracle is still possible," 32-year-old shop worker Ersin Avci had told AFP in Istanbul while voting continued.

"We still have a bit of hope that we will win and get our Turkey back." 

But as the first ballot boxes were emptied for the count at an Istanbul school used as a polling station, a heavy silence descended on the mostly CHP observers in the room.

The tension was palpable. Halis Firet, a CHP election observer at the polling station in one of Istanbul's pro-opposition neighbourhoods, said emotions ran so high during the vote that police had to intervene.

A police car remained parked in the school courtyard to survey the scene during the tallying of votes.

"We've called on everybody to calm down before the counting," said Firet, a 56-year-old painter.

- 'No hope' -

A monotonous blanket of grey cloud hung over Istanbul throughout Sunday, a reflection of the opposition's gloomier spirits for Turkey's first ever runoff election.

Rain began to fall just before the first official results came out giving Erdogan a sizeable lead.

At the CHP's Ankara headquarters, spokesman Faik Oztrak was in a sour mood during his first press conference of the evening.

He refused to take questions and left after a brief speech, a marked difference from his bullish remarks and vigorous contestation of the first-round vote count. 

Earlier on Sunday, queues at polling stations in opposition strongholds in Istanbul and Ankara seemed lower than in the first round, AFP journalists saw.

That boded ill for Kilicdaroglu, who needed to mobilise more voters, especially among the young and in Kurdish areas, to have any hope of defeating Erdogan.

"Today is not like the last time. I was more excited then. The outcome seems more obvious now," Bayram Ali Yuce, 45, said in one of Istanbul's heavily anti-Erdogan neighbourhoods.

In the Kurdish-majority city of Diyarbakir in the southeast, pessimistic housewife Fahriye Kacmaz lamented that nothing would change, even before the results emerged.

"We do not have any expectations. We actually have no hope... everything is useless," the 30-year-old told AFP.

- 'The right man' -

The scene outside Erdogan's presidential palace was a complete contrast, with joyful music booming out of loudspeakers and a huge Turkish flag unfurled as the president edged closer to victory.

Elated AKP voters congregated outside the building waving Turkish flags and banners bearing Erdogan's face while delighted motorists honked their car horns in a deafening crescendo audible from the CHP's base.

"Our people chose the right man. I expect Erdogan to add more to the good things he had already done for our country," 17-year-old Nisa Sivaslioglu told AFP in the Turkish capital.

The president addressed a rapturous audience in Istanbul after it became clear he had won a third mandate as president while celebratory fireworks exploded above.

In contrast, CHP supporters in Ankara had gathered outside their party's headquarters to watch the results trickle in on a big screen, their faces a picture of anxiety as their hopes ebbed with the setting sun.

With more than 99 percent of the ballots counted at around 9:00 pm (1800 GMT), official results showed Erdogan vanquishing his rival by 52 percent to 48 percent.

The opposition's dream was dead.

bur-imm/zak/lcm