Iran's President Hassan Rouhani has won re-election with a resounding 57 percent of the vote, the interior minister announced on Saturday.
Rouhani, a 68-year-old moderate cleric who spearheaded a 2015 nuclear deal with world powers, took 23.5 million votes -- 57 percent -- compared to 15.8 million - 38.3 percent - for hardline challenger Ebrahim Raisi.
Iranians flocked to the polls, with turnout hitting 73 percent.
Election organisers were forced to extend polling by several hours on Friday, as they struggled to adapt to a population explosion that has added 20 million names to the voting rolls in the past two decades.
"Already last night we had the feeling we were heading for a landslide, and it came true," said Farid Dehdilani, an adviser for the Iranian Privatisation Organisation, who worked on Rouhani's campaign.
"Our people reaffirmed their confidence in President Rouhani and their support for engagement with the world," he added.
Raisi, 56, had positioned himself as a defender of the poor and called for a much tougher line with the West.
But his revolutionary rhetoric and efforts to win over working class voters with promises of increased handouts gained limited traction.
"Rouhani's vote, particularly in rural areas, shows that Iranian people no longer believe in economic populism and radical change," said Ali Vaez, Iran analyst for the International Crisis Group, a think tank.
Russian President Vladimir Putin, a staunch ally of Iran in the Syrian conflict on the side of the Damascus regime, was among the first leaders to congratulate Rouhani.
EU foreign policy chief Federica Mogherini also tweeted her congratulations and vowed to work for greater "engagement, regional peace... (and the) expectations of people in Iran."
Both Russia and the European Union are eager to safeguard the 2015 deal which they signed alongside the United States, easing sanctions on Iran in exchange for curbs to its nuclear programme.
