Millions of voters across Iran are casting their ballots in the country’s presidential elections.
Although all six candidates are seen as conservatives, one of them, cleric Hassan Rouhani, has been reaching out to the reformists in recent days.
The BBC says the election will decide a successor to outgoing leader Mahmoud Ahmadinejad.
His eight years in power have been characterised by economic turmoil and Western sanctions against Iran over its controversial nuclear programme.
Polls across Iran opened at 08:00 local time (03:30 GMT) and are due to close at 18:00 (13:30 GMT). Some 50 million people are eligible to cast their ballots.
The past week brought a surprising change to what otherwise had looked like being a predictable election, the BBC reports.
Mr. Rouhani has been attracting increasing attention, speaking publicly about the need to re-engage with the West.
He has also promised to free political prisoners and called for greater reform of the media.
The surge of support for him came after Mohammad Reza Aref, the only reformist candidate in the race, announced on Tuesday that he was withdrawing his candidature on the advice of pro-reform ex-President Mohammad Khatami.
Mr. Rouhani now has the endorsement of two ex-presidents, Mr. Khatami and Akbar Hashemi Rafsanjani, who was disqualified from the race by the powerful Guardian Council.