Very early, partial results put a moderate candidate backed by reformists ahead in Iran's presidential election as vote-counting continued Saturday, as all six contenders called for calm during the count.
Hassan Rowhani, a former nuclear negotiator, had grabbed more than 46 percent of 861,866 votes counted by 6:00 am (0130 GMT), some seven hours after polls closed in Tehran on Friday.
More than 50.5 million Iranians were eligible to vote and elections officials said they were expecting a high turnout.
The partial figures were released by Interior Minister Mostafa Mohammad Najjar, who told state television his electoral staff would not "compromise accuracy for speed."
On those figures, Rowhani is followed by Tehran mayor Mohammad Baqer Qalibaf with 14 percent; top nuclear negotiator Saeed Jalili with 13 percent; and ex-commander of the Revolutionary Guards Mohsen Rezai with 12 percent. All three of these candidates hail from conservative camps.
Iranian authorities and media reported a massive turnout in Friday's election to find a successor to President Mahmoud Ahmadinejad.
Before the polls closed, all six of the presidential candidates issued a joint appeal for calm.
"We ask people not to pay attention to rumours of victory parades being organised and to avoid gathering before the official results" are announced by the interior ministry, their statement said.
In 2009, when Ahmadinejad's controversial re-election sparked months of mass protests that culminated in the detention of two of his challengers.
Electoral officials said the count got under way shortly after polls closed in the provinces at 10:00 pm (1730 GMT), the ISNA news agency reported.
Polling hours had been extended a further hour in the capital in the face of what officials reported was a turnout almost as large, or bigger, than that for the controversial re-election of Ahmadinejad four years ago.
Iranian media quoted the capital's top electoral official, Safar Ali Baratlou, as saying that as of 1400 GMT, "turnout (in Tehran province) is higher than four years ago. It will certainly reach 70 percent."
Officials in several other provinces reported turnout of at least 70 percent by 1330 GMT.
In 2009, turnout reached 85 percent nationwide.
More than 50.5 million Iranians were eligible to vote for the man -- no women candidates were allowed -- to succeed Ahmadinejad, who is constitutionally barred from standing for a third term.
Supreme leader Ayatollah Ali Khamenei, who has the ultimate say in all of the most sensitive issues including nuclear policy, had called for a large turnout and himself voted early.
Khamenei also attacked the United States for questioning the poll's legitimacy.
"The Iranian people... will do what is in their interest," Khamenei said on national television.
His remarks were echoed by Ayatollah Ahmad Janati, head of the Guardians Council electoral watchdog, who said voters "were poking their fingers in the eye of the enemy".
The full results are expected on Saturday, but if no candidate secures more than half of the votes for an outright victory, the top two will square off in a second-round run-off on June 21.
With the conservative camp divided, reformists seem confident of a good showing by Rowhani, a moderate cleric.
Under Ahmadinejad's reformist predecessor Mohammad Khatami, he headed Iran's nuclear negotiating team. Analysts say he has emerged as a frontrunner with a real chance of forcing a run-off.
Both sides, reformist and conservative, urged a high turnout.
"It's a duty," said one 50-year-old woman, who declined to give her name.
"I hope the next president can do something for us, and for the workers. I will vote for Qalibaf because he is a good mayor. I hope the promises he made will come true."
Former president Akbar Hashemi Rafsanjani, who was disqualified from standing and has thrown his weight behind Rowhani, urged a large turnout.
"We hope the election result will lead to national cohesion... since cohesion is a requirement for success against foreign and domestic dangers," he said.
A major factor will be the number of abstentions: many people were demoralised in 2009 when Ahmadinejad's re-election was widely claimed to be fraudulent.
That led to massive street demonstrations, which were crushed by the regime with deadly force. Two reformist candidates -- Mir Hossein Mousavi and Mehdi Karroubi -- were put under house arrest.
Many posters on Internet social networks, blocked after they were used to rally protests against Ahmadinejad's re-election, have urged abstentionists not to waste their votes this time.
The campaign has been dominated by Iran's controversial nuclear programme and an economy devastated by harsh EU and US sanctions imposed in an attempt to rein it in.
Inflation is raging at more than 30 percent, the rial has lost nearly 70 percent of its value and unemployment is rising.
Western governments and arch-foe Israel accuse Iran of seeking to develop atomic weapons under cover of its civil nuclear programme, a charge it vehemently denies.