Swedbank, which is already conducting an internal investigation into suspected money laundering, said it was not aware of such a violation.

The allegation risks opening a new front in a scandal which has hammered Swedbank's shares and rocked the region's banks.

Swedbank shares were down 3.8% at 1110 GMT after SVT aired an investigative program which cited a list of transactions between Swedbank's Baltic branch and bank accounts in the United States provided by an unidentified Wall Street source.

The Swedish bank is already under investigation by U.S. authorities for its role in the Baltic moneylaundering scandal, but the new information risks exposing Swedbank to greater scrutiny from the United States.

U.S. authorities have levied billions of dollars in fines against European banks for illegal financial transactions that have violated its sanctions against a range of countries.

SVT alleged Swedbank transferred more than 1 million euros ($1.1 million) from Kalashnikov Group to a U.S. subsidiary via the business network of a Russian oligarch who is a shareholder in the Russian arms firm.

Henriksson told SVT that Swedbank's own internal investigation is expected to be concluded in early 2020 and its conclusions "will be communicated", without specifying when.

Kalashnikov's Russia-based parent company was put on a U.S sanctions list after Russia annexed Crimea from Ukraine in 2014.

SVT said Kalashnikov's U.S-based subsidiary is permitted to sell arms it produces in the United States on condition it receives no financial transfers from its parent firm.

A Kalashnikov spokeswoman declined to comment.

Swedbank has lost around 40% of its market value since allegations surfaced that its Estonian branch processed suspect gross transactions of up to 20 billion euros a year from mostly Russian non-residents between 2010 and 2016.

The scandal started with Danske Bank, Denmark’s biggest bank. It is under investigation in several countries over 200 billion euros ($220 billion) in suspicious payments moved through its Estonian branch between 2007 and 2015 in one of the largest money laundering scandals in history.

"I'm going to take this information and give it to our investigators and we'll take a closer look at it," Henriksson said, while not confirming the existence of such customers.

In October, the Estonian state prosecutor said it was opening a criminal investigation into Swedbank.

(Additional reporting by Anna Ringstrom; editing by John O'Donnell, Mark Potter and Alexander Smith)

By Colm Fulton and Johan Ahlander