By Bozorgmehr Sharafedin
LONDON (Reuters) - Iranian opposition figure Mehdi Karoubi, under house arrest since 2011, announced his support for President Hassan Rouhani who is seeking a second term in Friday's election.
Rouhani, in a speech on Monday, told supporters he needed a strong mandate to push for political freedoms and the release of opposition leaders.
Karoubi, 80, and fellow reformist Mirhossein Mousavi ran for election in June 2009 and became figureheads for Iranians who protested against the vote they believed was rigged to bring back President Mahmoud Ahmadinejad.
Karoubi, Mousavi and Mousavi's wife Zahra Rahnavard were confined to their homes in February 2011 after the opposition leaders called supporters to rally in solidarity with uprisings in Arab countries.
"This election is a real confrontation between a real Islamic Republic and a ceremonial one," Karoubi was quoted as saying on Monday by Saham News, the official website of his political party.
Karoubi asked all Iranians to take part in the election and to protect the democratic process by choosing their preferred candidate, but said: "I will vote for Rouhani."
Rouhani, a pragmatist Muslim cleric, was elected in 2013 by 51 percent of votes on promises to ease Iran's international isolation and end the house arrest of opposition leaders.
He reached a deal with world powers in 2015 which lifted most international sanctions in return for curbing Iran's nuclear programme.
"But there are issues that my legal government was not able to resolve," Rouhani said on Monday, according to state media, in a speech in the city of Tabriz, referring to his failure to end the house arrest.
"Some issues cannot be resolved if the government has only 51 percent of votes."
Rouhani is standing against five other candidates, mostly hardliners, on May 19, with a run-off a week later if no candidate wins more than 50 percent of votes in the first round.