Iranian President Mahmoud Ahmadinejad has fired Foreign Minister Manouchehr Mottaki, Iran’s official Irna news agency reports.
Initial reports gave no reason for the decision.
There had been no indication Mr Mottaki, a key figure in Iran’s nuclear negotiations with the West, was about to lose his job.
News reports suggest Mr Ahmadinejad has appointed the country’s top nuclear official to replace Mr Mottaki.
State television reported Ali Akbar Salehi, head of Iran’s Atomic Energy Organisation and a close ally of the president, would take over in a caretaker capacity.
Analysts say Mr Mottaki’s dismissal may be part of a political power play between conservatives and liberals in Iran.
“I appreciate your diligence and services as the foreign minister,” said Mr Ahmadinejad in a letter to Mr Mottaki, Mehr news agency reported.