A judge overseeing the fraud and money laundering case involving former International Monetary Fund chief Rodrigo Rato has ordered him to put up 18 million euros ($20 million) as collateral to unblock his financial accounts.

Rato headed the IMF from 2004 to 2007 and is a historic figure in Spain's ruling Popular Party, which has been hit hard by the case ahead of nationwide regional and local elections this Sunday.

The judge set the amount Thursday, a month after Rato's accounts were frozen by court order following his brief detention amid a police search of his home and office.

Rato was economy minister under conservative ex-Prime Minister Jose Maria Aznar between 1996 and 2004, and had been seen as a possible successor.

Rato headed the IMF from 2004 to 2007.