- The banks included Bank of America, Morgan Stanley and Goldman Sachs
- Europe's Barclays, Societe Generale and BNP Paribas were also downgraded
- Last month, Standard & Poor's downgraded the credit ratings of 15 banks
The ratings firm Fitch downgraded a cluster of the world's largest banks Thursday, pointing to trading challenges facing international markets.
The banks included Bank of America, Morgan Stanley and Goldman Sachs, as well as Europe's Barclays, Societe Generale and BNP Paribas.
Germany's Deutsche Bank and Switerzland's Credit Suisse were also downgraded.
It was the third major credit rating agency to downgrade global financial institutions since September.
"These actions culminate a broader, global review of financial institutions," the ratings firm said in a written statement.
Managing Director Thomas Abruzzo added that the downgrades reflect "fundamental risks in the global trading bank environment."
He noted that, for Bank of America, Thursday's move reflects "particularities of the firm's business," notably issues arising from "legacy acquisitions" such as Merrill Lynch and Countrywide.
Last month, Standard & Poor's downgraded the credit ratings of 15 banks.
In September, Moody's Investors Services also announced downgrades.
Financial institutions have faced difficult times worldwide, with investor concerns largely focused on the exposure banks may have to the European debt crisis.