The Frankfurt-listed shares of U.S. banks Citigroup and Bank of America fell on Friday, with traders and analysts citing fears that big U.S. banks could be nationalized.

At 1130 GMT, Citigroup shares were down 6.4 percent in Frankfurt and Bank of America traded 8.0 percent lower. Spokesmen for both banks in London declined to comment.

Spokesmen for the banks in New York were unavailable for comment.

People believe that big U.S. banks will be nationalized as will a lot of western banks in general, and that there will be a lot of capital raising to come, said Mark Sartori, head of trading at Fox-Pitt, Kelton in London.

Barclays Wealth in a global daily note said falling bond yields in the United States probably reflect a rumor in markets that two American banks risk being nationalized overnight.

(Reporting by Sitaraman Shankar, Dominic Lau and Olesya Dmitracova in London and Peter Starck in Frankfurt)