Iran’s President-elect Masoud Pezeshkian has vowed to “serve all Iranians” in a victory speech.

Mr Pezeshkian, a reformist candidate, spoke at the the mausoleum of the late Grand Ayatollah Ruhollah Khomeini, the leader of the 1979 Islamic Revolution, addressing journalists in a chaotic event.

The heart surgeon said: “In this election, I didn’t give you false promises. I did not lie.

“It’s been many years after the revolution that we come to the podium, we make promises and we fail to fulfil them. This is the biggest problem we have.”

Mr Pezeshkian bested hard-line former nuclear negotiator Saeed Jaili in Friday’s run-off election.

A woman casts her vote for the presidential election
Iran held a run-off election that pitted a hard-line former nuclear negotiator against a reformist (AP)

Meanwhile, the United States said the Iranian poll was neither free nor fair, saying it likely would not change the Islamic Republic’s stance on human rights.

The US state department said it would continue to use diplomacy with Tehran “when it advances American interests”.

“The elections in Iran were not free or fair. As a result, a significant number of Iranians chose not to participate at all,” the state department said.

“We have no expectation these elections will lead to fundamental change in Iran’s direction or more respect for the human rights of its citizens. As the candidates themselves have said, Iranian policy is set by the supreme leader.”

It added: “The elections will not have a significant impact on our approach to Iran, either. Our concerns about Iran’s behaviour are unchanged.”

Mr Pezeshkian clenches his fist after casting his vote
The election comes during a particularly volatile time in the Middle East (AP)

Mr Pezeshkian promised no radical changes to Iran’s Shia 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.

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 with enough of a stockpile to produce several nuclear weapons if it chose.

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.

Overall, Iran’s interior ministry said 30 million people voted in an election held without internationally recognised monitors, representing a turnout of 49.6% – higher than the historic low of the June 28 first round vote but lower than other presidential races.

Supporters of Mr Pezeshkian entered the streets of Tehran and other cities before dawn to celebrate as his lead grew over Mr Jalili.

The defeated candidate, Saeed Jalili
Mr Jalili is Iran’s former top nuclear negotiator (AP)

Mr Pezeshkian’s win still sees Iran at a delicate moment, with tensions high in the Middle East and a looming election in the United States that could put any chance of a detente between Tehran and Washington at risk.

The victory also was not a rout of Mr Jalili, meaning he will have to carefully navigate Iran’s internal politics as the doctor has never held a sensitive, high-level security post.

Government officials up to Khameni, the supreme leader, predicted higher turnout as voting got under way, with state television airing images of modest lines at some polling centres. However, online videos purported to show some polls empty while a survey of several dozen sites in Tehran saw light traffic and a heavy security presence on the streets.

Authorities counted 607,575 voided votes – which often are a sign of protest by those who feel obligated to cast a ballot but reject both candidates.

Khamenei praised the turnout on Saturday despite what he alleged was a boycott campaign “orchestrated by the enemies of the Iranian nation to induce despair and a feeling of hopelessness”.

Election officials count ballots
Turnout was recorded at 49.6% (AP)

He added: “I would like to recommend Dr Pezeshkian, the elected president, put his trust in God, the Compassionate, and set his vision on high, bright horizons.”

Voters expressed a guarded optimism.

“I don’t expect anything from him — I am happy that the vote put the brake on hard-liners,” said bank employee Fatemeh Babaei, who voted for Pezeshkian. “I hope Pezeshkian can return administration to a way in which all people can feel there is a tomorrow.”

Mr Pezeshkian, who speaks Azeri, Farsi and Kurdish, campaigned on outreach to Iran’s many ethnicities. He represents the first president from western Iran in decades – something people hope will aid the county as those in the western part are considered more tolerant because of the ethnic and religious diversity in their area.

The election came amid heightened regional tensions. In April, Iran launched its first-ever direct attack on Israel over the war in Gaza, while militia groups armed by Tehran – such as the Lebanese Hezbollah and Yemen’s Houthi rebels – are engaged in the fighting and have escalated their attacks.

While Khamenei remains the final decision-maker on matters of state, Mr Pezeshkian could bend the country’s foreign policy toward either confrontation or collaboration with the West.

Crown Prince Mohammed bin Salman of Saudi Arabia, which has reached a detente with Iran, sent his congratulations to Mr Pezeshkian that stressed his “keenness to develop and deepen the relations that bring our two countries and peoples together”.

Russian President Vladimir Putin, who has relied on Iranian-made drones in his war on Ukraine, similarly congratulated Mr Pezeshkian.