Tehran: Moderate cleric Hassan Rouhani had 51 per cent of votes in the Iranian presidential election after a count of 32 million votes, state television said on Saturday.
If the result remains the same when all the votes are counted, Rouhani will win the election outright and avoid a second-round run-off. Iran has a total electorate of some 50 million and officials have said the turnout in Friday's poll topped 70 per cent.
Rouhani had 50 per cent of the vote, more than three times as many as his nearest rival, conservative Tehran mayor Mohammad Baqer Qalibaf.
Under Iranian law, any candidate must clear a threshold of 50 per cent plus one vote to avoid having to face the second-placed candidate in a run-off, which would be held on June 21.
More than 50.5 million Iranians were eligible to vote to find a successor to Ahmadinejad, who after serving two consecutive terms was constitutionally barred from standing for office again.
And voters reportedly turned out in massive numbers for Friday's election, with Rouhani benefitting from the withdrawal this week of the only moderate candidate Mohammad Reza Aref.
Aref, a former first vice president, pulled out of the race on Tuesday at the urging of former reformist president Mohammad Khatami, who then threw his weight behind the 64-year-old moderate cleric.
Rouhani, a former top nuclear negotiator who has vowed to mend Iran's ties with the international community, garnered nearly 6,049,655 votes from 12,091,699 ballots counted by 12:00 pm (0730 GMT), the interior ministry said on Saturday.
Rouhani led talks with world powers over Iran's controversial nuclear ambitions under Khatami's presidency.
During his tenure, in 2003, the Islamic republic agreed to suspend uranium enrichment. It was restarted after Ahmadinejad first became president in 2005.
Iran has been at loggerheads with world powers over its nuclear ambitions, which the West suspects is aimed at developing atomic weapons. The stand-off has resulted in the imposition of harsh economic sanctions and Tehran's international isolation.
While campaigning, Rouhani promised to move to ease those sanctions, which have led to severe economic pain in the country.
Inflation is raging at more than 30 per cent, the Iranian currency, the rial, has lost nearly 70 per cent of its value, and unemployment is rising.
On the votes counted so far, Rouhani is followed by Qalibaf with 15 per cent; ex-commander of the Revolutionary Guards Mohsen Rezai with 12.5 per cent; top nuclear negotiator Saeed Jalili with 11.5 per cent. All three hail from conservative camps.
Jalili, Qalibaf and ex-former foreign minister Ali Akbar Velayati, another candidate who is behind with only six per cent of the votes so far, are all considered close to supreme leader Ayatollah Ali Khamenei.
Rouhani, who boasts of close relations with moderate ex-president Akbar Hashemi Rafsanjani, also touts his relation with Khamenei, who has final decision on all key state issues, including the nuclear programme.
Rouhani represented Khamenei in the Supreme National Security Council, Iran' top security body, where he also served as its secretary for 16 years until 2005.
In the run-up to the disputed re-election of Ahmadinejad in 2009, official election results were quickly released. But in this campaign, counting of the votes has proved to be time consuming.
Interior Minister Mostafa Mohammad Najjar said early on Saturday that his electoral staff would not "compromise accuracy for speed".
Abbas Ali Kadkhodaei, the spokesman for the Guardians Council electoral watchdog, said late Friday that "no violation" had been reported whatsoever across Iran.
Ahmadinejad's re-election in 2009 sparked massive anti-regime street protests after his opponents and two reformist candidates Mir Hossein Mousavi and Mehdi Karroubi alleged wide-scale voting fraud.
Those protests, stifled by a brutal regime crackdown, led to the eventual detention under house arrest of Mousavi and Karroubi, and a widespread suppression of reformists.
Rouhani's surge in the campaign came after Khatami publically endorsed him, asking all his supporters to vote for the moderate candidate.
Khatami's endorsement also gave birth to an online movement, with social networkers urging abstentionists not to waste their votes this time around.
"I will vote for Rouhani, even though I do not know him at all and did not want to vote until yesterday," said a man named Ali on his Facebook page.
"I will vote because the consensus of those wanting to save Iran is on Rouhani."
Other net surfers have adopted Rouhani's official colour - purple - and his symbol of a key to open the door to solutions for Iran's problems.