Nigeria’s central bank governor Lamido Sanusi has been suspended by the president for “financial recklessness and misconduct”.
Mr Sanusi caused shockwaves in Nigeria when he alleged that $20bn (£12bn) in oil revenue had gone missing.
Nigeria’s state oil firm has denied failing to account for the money, saying the claim was “unsubstantiated”.
Mr Sanusi is widely respected after undertaking reforms to the banking sector since his appointment in 2009.
He was named central bank governor of the year for 2010 by Banker magazine.
He told the BBC he would challenge his suspension in order to preserve the central bank’s independence.
“I’m proud of my own record,” he said.
Foreign exchange, bond and money markets have stopped trading because of uncertainty caused by the move, Reuters news agency reports.