Tafa Balogun has been taken in for questioning by Nigeria's anti-graft watchdog, the Economic and Financial Crimes Commission (EFCC).

Mr Balogun, who denies wrongdoing, is expected to appear in court shortly.

Nigeria has vowed to crush corruption as it seeks to convince foreign creditors to ease its debt burden, our correspondent reports.

Mr Balogun stepped down after the EFCC revealed it was investigating large sums of money held in Lagos bank accounts linked to him.

Mr Balogun's lawyer told the BBC he has not seen his client since his detention on Monday night.

Corruption fight

Last week, President Olusegun Obasanjo announced the sacking of his education minister, Fabian Osuji, in a televised broadcast.

The president accused Mr Osuji of offering a bribe of 55m naira ($417,000) to senate president Adolfus Wabara as he tried to secure a bigger budget for his ministry.

Mr Osuji has said he will sue the government over his televised dismissal, claiming it violated his human rights.

The ruling PDP party is meeting on Wednesday to discuss Mr Wabara's alleged role in the scandal.

Oil-rich Nigeria is trying to shake off its reputation as one of the world's most corrupt countries.

However, President Obasanjo's earlier failures to match tough words with action have diluted the impact of the latest move, according to the BBC's Anna Borzello in Lagos.

The EFCC estimates 45% of Nigeria's oil revenues are wasted, stolen or siphoned away by corrupt officials.