Reformist candidate Masoud Pezeshkian won Iran’s runoff presidential election on Saturday, defeating hard-liner Saeed Jalili by promising to reach out to the West and ease enforcement on the country’s mandatory headscarf law.

A vote count offered by authorities put Mr Pezeshkian as the winner with 16.3 million votes to Mr Jalili’s 13.5 million in Friday’s election.

“By gaining majority of the votes cast on Friday, Pezeshkian has become Iran’s next president,” the interior ministry said on Saturday.

Mr Pezeshkian promised no radical changes to Iran’s Shiite theocracy in his campaign and long has held Supreme Leader Ayatollah Ali Khamenei as the final arbiter of all matters of state in the country. 

However, the president has vowed to revive the flagging economy, beset by mismanagement, state corruption and US sanctions.

“If I try but fail to fulfill my campaign promises, I would say goodbye to political work and not continue. There is no point in wasting our life and not being able to serve our dear people,” Mr Pezeshkian said in a video message to voters.

But even Mr Pezeshkian’s modest aims will be challenged by an Iranian government still largely held by hard-liners, the ongoing Israel-Hamas war in the Gaza Strip, and Western fears over Tehran enriching uranium to near-weapons-grade levels.

Supporters of Mr Pezeshkian, a heart surgeon and longtime lawmaker, entered the streets of Tehran and other cities before dawn to celebrate as his lead grew over Mr Jalili, a hard-line former nuclear negotiator.

The election, called early after the death of president Ebrahim Raisi in a helicopter crash, followed a first round marked by a historically-low turnout last week.

The first round of voting June 28 saw the lowest turnout in the history of the Islamic Republic since the 1979 Islamic Revolution. 

Government officials predicted a higher participation rate as voting got under way, with state television airing images of modest lines at some polling centres across the country.

However, online videos purported to show some polls empty while a survey of several dozen sites in the capital, Tehran, saw light traffic amid a heavy security presence on the streets.

More than 61 million Iranians over the age of 18 were eligible to vote, with about 18 million of them between 18 and 30.

Voting was to end at 6pm, but was extended until midnight to boost participation.