US authorities are investigating UniCredit's German unit HVB as part of a global crackdown on possible violations of sanctions on Iran that has already cost Standard Chartered a hefty settlement.
In an emailed statement on Sunday, UniCredit said the New York County District Attorney's Office, the US Department of Justice and the US Treasury Department's Office of Foreign Assets Control were leading the investigation.
The bank was responding to an earlier report in the Financial Times.
The statement did not mention a particular country but a person familiar with the situation said the investigation involved possible breaches of Iran sanctions.
UniCredit said HVB was conducting a broader review of its historic compliance with US economic sanctions on its own initiative. HVB declined to comment beyond the statement.
"The investigation and review are ongoing, and it would be inappropriate to comment further at this time," UniCredit said.
US authorities have been investigating a number of banks for allegedly moving billions of dollars in Iran-linked transactions. British bank Standard Chartered this month reached a $340 million settlement after the New York Department of Financial Services accused it of concealing $250 billion in Iran transactions.
Separately, US authorities are investigating Royal Bank of Scotland, and Germany's second-largest lender Commerzbank.
Commerzbank warned last week it faced a financial hit to settle the US probes into violations of sanctions on Iran and other countries, which could exceed provisions.
UniCredit mentioned the US probe in a 463-page prospectus for a capital increase in January and in its following financial earnings statements.
The documents however mentioned neither HVB, the German bank UniCredit acquired in 2005, or Iran. These details were first reported by the Financial Times on Sunda.