Reformist-backed cleric Hassan Rohani has won Iran's presidential election, the interior ministry has confirmed, scoring a surprise outright victory over conservative hardliners.
Mr Rohani secured just over 50% of the vote, avoiding the need for a run-off in the election to choose a successor to Mahmoud Ahmadinejad, who was not eligible to stand for a third term.
A former chief nuclear negotiator known for his conciliatory approach, Mr Rohani has pledged to try to ease international sanctions imposed on Iran over its nuclear programme.
While the president runs the economy and wields important influence in day-to-day decision-making, Supreme Leader Ayatollah Ali Khamenei has the final say on major issues including national security and Iran's nuclear program.
Washington and its Western allies accuse Tehran of pursuing nuclear weapons and have imposed sanctions on Iran that have damaged its economy and triggered a rise in inflation and unemployment. Tehran says its nuclear program is peaceful and aimed at generating power.
Mr Rohani has said he will promote a policy of constructive interaction with the world, but not surrender to Western demands for a nuclear suspension, and will enact a domestic civil rights charter.
Mr Rohani rose to international prominence as Iran's nuclear negotiator in talks with Britain, France and Germany from 2003 to 2005, Reuters reports. The negotiations saw Iran agree to suspend nuclear fuel enrichment-related activities, tamping down Western pressure on Tehran.
He left the post when Mahmoud Ahmadinejad came to office in 2005. Tehran relaunched and expanded uranium enrichment, and there has been no substantive progress in intermittent negotiations with six world powers since then.
The United States urged Iran's leadership to heed the will of the Iranian people following the presidential election.
The White House said the United States remained ready to engage the Iranian government directly to reach a diplomatic solution to address concerns from the international community about its nuclear program.
Mr Rohani's nearest rival in Friday's election was conservative Tehran mayor Mohammad Baqer Qalibaf, a long way behind with less than 16% of the vote.
Other hardline candidates close to Ayatollah Khamenei, including current nuclear negotiator Saeed Jalili, scored even lower.
Turnout was estimated at just over 72% of the 50 million Iranians eligible to vote.