Hasan Rouhani has taken his oath of office, the final step in his inauguration as Iran's new president.

Rouhani, who replaces Mahmoud Ahmadinejad, was sworn in during an open session of parliament on Sunday. State TV broadcast the ceremony live.

Iran's media and officials have treated Rouhani as president since Saturday, when he was endorsed by the country's Supreme Leader Ayatollah Ali Khamenei.

Leaders and other representatives from more than 50 countries, mostly from the region, attended the ceremony.

It was the first time since Iran's 1979 Islamic Revolution that foreign dignitaries attended the swearing-in ceremony of an Iranian president, underscoring Rouhani's stated commitment to improving the country's foreign ties.

Rouhani won a landslide victory in June 14 presidential elections.