Cleric Hassan Rouhani has officially replaced Mahmoud Ahmadinejad as president of Iran. Mr Rouhani's election has been endorsed by Supreme Leader Ayatollah Ali Khamenei at a ceremony in the capital, Tehran. He won the presidential poll in June, promising to reform and to put an end to Iran's international isolation. The ceremony marks the handover of power, but his public inauguration does not take place until Sunday. The 64-year-old is a former nuclear negotiator for Iran and was an Islamic activist before the 1979 Revolution.