Iyabo Obasanjo-Bello, a serving senator, appeared in court in the capital Abuja on Monday after weeks in hiding. She was charged last month with two former health ministers and nine other officials with embezzling 470 million naira of public money.

Obasanjo-Bello pleaded not guilty to charges that she illicitly received 10 million naira of the money.

"The matter has been adjourned to May 21 for arguments on bail application. In the meantime, the accused should be remanded at Maitama police station," Judge Salifu Garba told the High Court in Abuja.

President Umaru Yar'Adua, who took over from Obasanjo a year ago after winning a turbulent election, has pledged a campaign of "zero tolerance" against graft in Africa's top oil exporter, ranked among the world's most corrupt states.

There have been calls for Obasanjo himself to appear before a parliamentary commission probing allegations that billions of dollars were squandered on unfinished power projects during his eight-year tenure.

An investigation was also launched last month into his management of the country's mainstay oil and gas industry.

Obasanjo-Bello, who chairs the Senate health committee, is the first member of Obasanjo's family to face graft charges since he stepped down.

She has denied any wrongdoing, telling Nigerian media she collected the money to pay for the travel expenses of Senate health committee members for a visit to Ghana.

She failed to appear in court on April 8 to face the charges and had refused to be questioned by the Economic and Financial Crimes Commission (EFCC).

The two ex-ministers charged in the case were forced to resign in March, a month after the scandal emerged, making them the first cabinet casualties of the new administration.

The former ministers and nine other top health officials all pleaded not guilty to the 54-count charges brought by the EFCC, which in total bring the amount of money allegedly embezzled to 471 million naira.