"We have been observing the development of market interest rates and cash-deposits of certain clients, especially balances on current-accounts and cash-clearing accounts in interbank transactions for quite some time," the Swiss bank said in a statement after Switzerland's central bank disclosed negative interest rates earlier on Thursday.

"As a consequence, we've already levied fees to discourage interbank clients from holding excessive cash balances over the past two years."

The bank said it will continue to evaluate whether further measures such as fees or negative interest rates are necessary, although it currently qualifies for an exemption the Swiss National Bank has granted for banks based on their deposits held at the central bank.

(Reporting By Katharina Bart)

Stocks treated in this article : UBS AG, UBS Group AG