Ukrainian hackers collaborated with the country’s security services, the SBU, to breach Russia’s largest private bank, a source within the department confirmed to Recorded Future News.

Last week, two groups of pro-Ukrainian hackers, KibOrg and NLB, hacked into Alfa-Bank and claimed to obtain the data of more than 30 million customers, including their names, dates of birth, account numbers, and phone numbers, according to a post on their official website.

Alfa-Bank was sanctioned by the United States following Russia’s invasion of Ukraine last year. The bank is owned by the Russian-Israeli billionaire Mikhail Fridman, who is blacklisted by the U.S. and Europe as part of efforts to impose restrictions on Russia’s economy and its wealthiest businessmen.

Hackers released (ZIP) some of the data online, including information about Fridman and his son, pro-Russian blogger Artemy Lebedev, and Russian rappers Timati and Basta. Alfa-Bank denied reports of the leak, according to Russian news agency TASS.