UniCredit said on Monday it was challenging the terms set by the European Central Bank (ECB) for the Italian bank to cut its exposure to Russia, and seeking a ruling from the European Union's General Court, as well as a freezing of the request in the meantime.

Euro zone banks still involved with Russia more than two years after Moscow invaded Ukraine have come under growing pressure in recent weeks from the bloc's supervisors, as well as U.S. authorities, over their ties to the country.

A complex regulatory backdrop, involving Western sanctions against Moscow and local laws in Russia where the Italian group runs a retail bank, meant it had to "seek clarity and certainty" on the actions it needed to take, UniCredit said in a statement two and a half years after Russia's full scale invasion of Ukraine.

After Austria's Raiffeisen, UniCredit has the biggest exposure to Russia, where it runs a top 15 bank, among European lenders.

Raiffeisen has no plans to take legal action against the ECB over the request to reduce its Russia-related business, a spokesperson has said.

"For anyone who believes that Ukraine's fight against Russia is important for the security of Europe, the fact that UniCredit stayed in Russia, made profits, and is now suing the ECB over their attempts to get it to leave, this doesn't look good," said Nicolas Veron of Brussels think tank Bruegel.