Iranians will go to the polls on June 14 next year to elect a successor to President Mahmoud Ahmadinejad who is in his second and final term, the interior ministry announced on Friday.
The presidential election will be held alongside municipal polls, a ministry statement carried by the official IRNA news agency said.
The last presidential election in 2009, which saw Ahmadinejad declared the winner over allegations by his challengers of fraud, was followed by widespread protests that were brutally crushed by authorities.
The figureheads of the opposition "Green Movement" -- former prime minister Mir Hossein Mousavi and former parliament speaker Mehdi Karoubi -- have languished under house arrest ever since.
On a visit to Tehran at the end of last month, UN chief Ban Ki-moon called on Iran to free all its political prisoners, adding that allowing the people's voice to be heard was especially important ahead of the presidential election.
"I have urged the authorities during my visit this time to release opposition leaders, human rights defenders, journalists and social activists to create the conditions for free expression and open debate," Ban said, according to the text of the address delivered to an Iranian diplomats' college.
"Restricting freedom of expression and suppressing social activism will only set back development and plant the seeds of instability," he warned.