Iran presidential election
Iran's Supreme Leader Ayatollah Ali Khamenei speaks to the audience in Tehran Handout via Reuters

Iranians are heading to the polls in a crucial presidential election to choose the 12th president of the theocratic nation. In the closely fought race, four candidates approved by the powerful clerical body, Guardian Council, are vying for the post including the incumbent, Hassan Rouhani.

More than 63,500 polling stations are set up across the country with nearly 56 million Iranians eligible to cast the ballot. Polls opened at 8am on Friday, 19 May, and images released by state-run news outlets show brisk voting in the morning. Results are expected to be announced within 24 hours after polling closes at 6pm. Polling is usually extended up to midnight if there is a high turnout.

Arrangements are in place in more than 100 countries for Iranian expats to cast their votes. Besides the presidential election, voting also takes place for village and city councils.

The main challenge for Rouhani, a 68-year-old moderate cleric, is from Ebrahim Raisi, 56, who is seen close to Supreme Leader Ayatollah Khamenei and also the influential, Revolutionary Guards. A presidential run-off will take place if none of the contenders manages to secure 50% of the vote. All the presidential candidates in the past have secured a second term in Iran.

Though six candidates were ratified by the Guardian Council, two of them dropped out later. Mostafa Hashemitaba, a reformist, and Mostafa Mirsalim, an ultra-conservative figure are among the four who are in the race.

"Everyone should vote in this important election... vote at early hours. The country's fate is determined by the people," Khamenei, who wields the highest political authority, said shortly after casting the vote.

Hailing the presidential elections as an "important" event not just for Iran but also the entire Middle East, Khamenei had earlier said: "Regional nations have pinned their eyes, with praise and envy, on people's turnout in the Friday election to once again witness the grandeur of the Iranian nation, the freedom of the Islamic establishment and the religious democracy."