Fitch Ratings downgraded on Tuesday its rating on Italy's biggest bank UniCredit SpA and threatened rating cuts on seven other Italian banks and several Spanish and French banks following recent changes in its outlook on euro zone sovereign ratings.

The downgrade reflects the material market and fundamental challenges facing many banks globally, particularly in Europe, Fitch said in its statement on UniCredit.

UniCredit's long-term issuer default rating (IDR) has been cut to 'A-', from 'A', and the short-term IDR to 'F2', from 'F1', with the ratings kept on 'watch negative', the agency said in a statement.

The seven Italian banks put on 'watch negative' by Fitch include its largest retail lender Intesa Sanpaolo , the country's third-biggest lender Banca Monte dei Paschi di Siena and UBI Banca .

Intesa currently has a long-term 'A' rating, BMPS 'BBB+', and UBI 'A-', Fitch said.

In Spain, the eight banks on 'watch negative' include Banco Santander , Banco Bilbao Vizcaya Argentaria and CaixaBank SA .

In France Fitch Ratings revised to 'negative' from 'stable' the outlook on Societe Generale , Groupe BPCE, Dexia Credit Local and La Banque Postale.

The move follows Fitch's decision last week to lower the outlook on France's triple-A sovereign rating to negative. Standard & Poor's put France and 14 other euro zone countries under review at the start of the month.

The head of French securities market regulator AMF said on Tuesday it would take a miracle for the country to keep its top-notch credit rating and warned of far-reaching effects for the euro zone's second-largest economy should it lose it.

In Belgium, Fitch said it could cut the ratings of KBC and Dexia Bank Belgium .

On December 16 Fitch put on 'watch negative' the sovereign ratings of Italy, Belgium, Spain, Slovenia, Ireland and Cyprus citing the adverse effect of the euro zone crisis on economic and financial stability.

(Writing by Nigel Tutt)