Moody's Investors Service cut the credit ratings of six German banking groups and Austria's three-largest banks today.

The agency said the banks face risks if the euro zone crisis deepens.

The cuts are part of a broad review of banks in the region that has had investors on edge but were mild when compared to cuts for banks in weaker economies such as Spain and Italy.

Moody's said German lenders face risks to the quality of their assets if the euro zone crisis deepens or the global economy slows more.

But it also noted the relative strength of the German and Austrian economies.

Commerzbank, Germany's second-largest lender, saw its long-term rating cut by one notch to A3 from A2 and assigned a negative outlook. Other German banks Landesbank Baden-Wuerttemberg and Norddeutsche Landesbank GZ were lowered to A3 from A2 and given stable outlooks while Italy's Unicredit saw its German unit cut to A3 from A2 and given a negative outlook.

The agency delayed action on Deutsche Bank and its subsidiaries, saying that will come with reviews for other global firms with large capital markets operations.

In Austria, Moody's cut the long-term rating for Erste Group Bank by two notches to A3 from A1 and assigned a negative outlook while UniCredit Bank Austria was cut to A3 from A2, also with a negative outlook. Raiffeisen Bank International was cut to A2 from A1 and assigned a stable outlook.

For the Austrian banks, Moody's noted vulnerabilities from operating conditions in Central and Eastern Europe and the Commonwealth of Independent States. It also noted limited loss-absorption capacities for both the German and Austrian banks.

Moody's said on April 13 it would begin issuing conclusions to various reviews for European banks and global financial securities firms, including big US investment banks. This process was to begin in mid-May and conclude by the end of June.