(Reuters) -- Spain's banks would need between 51 billion and 62 billion euros ($64 billion-$78 billion) in extra capital to weather a serious downturn of the economy and new losses on their books, two independent audits of the sector showed Thursday.

The results of the audit from consultancies Roland Berger and Oliver Wyman will now be used by the Spanish government to determine how much of 100 billion euros of available European funds it needs to recapitalize ailing lenders, and then to formalize an aid request to other euro zone countries.

The Bank of Spain said Thursday the 100 billion euro ($126 billion) bailout fund gives a wide margin to correct these capital needs.

It said Spain's three biggest banks would not need extra capital in a stressed scenario, noting that the problems are limited to a small group of Spanish banks for which the state has already started to act.

Spain's economy ministry said a more detailed audit would come in September.

Euro zone finance ministers met in Luxembourg to discuss how to channel the aid to Spanish lenders weighed down by bad debts from a burst property bubble. Madrid's economy minister said a formal request would be made in days for the bailout, which was agreed two weeks ago.

Many in the markets see the package as a mere prelude to a full program for the Spanish state, which Madrid vehemently denies it will need.

($1 = 0.7933 euros)

(Reporting By Julien Toyer and Nigel Davies; Writing by Tracy Rucinski; Editing by Paul Day)