Iran's president has fired the country's foreign minister, Manouchehr Mottaki, but no reason has immediately been given for the decision.
News reports suggest President Mahmoud Ahmadinejad has appointed the country's top nuclear official to replace Mr Mottaki.
State television reported that the head of Iran's Atomic Energy Organisation, Ali Akbar Salehi, a close ally of the president, would take over in a caretaker capacity.
The BBC reports there has been mutual distrust between the president and Mr Mottaki since the 2005 election that brought Mr Ahmadinejad to power.
Mr Mottaki was the campaign manager for one of Mr Ahmadinejad's rivals, Ali Larijani, and the two men are often described as part of a pragmatic conservative bloc that believes the president's radical agenda has made Iran more vulnerable.