TEHRAN: An Iranian opposition political party says its leader, who has been under house arrest without charges for the past four years, has undergone foot surgery for a broken bone.

Mahdi Karroubi, a parliament speaker in the 1990s, challenged the results of the 2009 presidential election that returned hard-liner Mahmoud Ahmadinejad to office.

Karroubi and another opposition leader, Mir Hossein Mousavi, were put under house arrest in 2011 amid the Arab Spring uprisings across the Middle East.

Karroubi's National Confidence Party on Tuesday quoted his son, Hossein, as saying the "surgery was successful." The party website says President Hasan Rouhani's brother, Hossein Fereidoun, visited Karroubi in hospital and wished him a speedy recovery.

It's the sixth surgery for Karroubi under arrest — he has also had heart, eye and back surgery.