Lamido Sanusi has spearheaded reforms in Nigeria's troubled banking sector since his appointment in 2009. Photo: BBC NEWS

President Goodluck Jonathan said there had been "far-reaching irregularities" under Mr Sanusi's watch.

BBC Abuja editor Bashir Saad Abdullahi says the allegation of missing oil revenue has come as a huge embarrassment for the government.

Nigeria's state oil firm has denied failing to account for the money.

The Nigerian National Petroleum Corporation said the allegations were "unsubstantiated" and showed "little understanding of the technicalities of the oil industry".

Mr Sanusi is currently in Niger attending a meeting of regional central bank heads.

President Jonathan asked him to resign in December but Mr Sanusi refused, sources told the BBC Hausa service.

The president does not have the power to sack the central bank governor - only the National Assembly can do this.

The presidential statement announcing his suspension said he had been removed pending "investigations into breaches of enabling laws, due process and mandate" of the Central Bank of Nigeria.

Mr Sanusi has spearheaded banking reforms since his appointment in 2009.

Our correspondent says news of his suspension could further damage the anti-corruption credibility of President Jonathan's administration.