A branch of Otkritie Bank, one of Russia's biggest private lenders, in central Moscow.

Andrei Makhonin | Contributor

A branch of Otkritie Bank, one of Russia’s biggest private lenders, in central Moscow.

Some of Otkritie’s shareholders are connected to major state entities, a fact that prompted some analysts to believe it was too big and influential to be allowed to fail.

The central bank did not say how much it was spending on the bailout, but said it planned to take a minimum 75 percent stake after evaluating Otkritie’s financial position. Until now, the biggest banking bailout in Russia was a 395 billion ruble ($6.7 billion) rescue of the Bank of Moscow in 2011, Russia’s fifth-biggest lender by assets at the time.

Otkritie Bank, part of the wider Otkritie Group, grew rapidly in recent years, snapping up banks such as Nomos, non-pension funds and insurers, and even the diamond business of Russian oil producer Lukoil.

But Dmitry Tulin, the central bank’s first deputy chairman, told a news briefing that its business practices had been questionable.

When asked whether market participants should be concerned about the news regarding a planned Otkritie bailout package, Gina Sanchez, CEO of Chantico Global, said that while Russia’s banking sector had not necessarily been a primary focus to date, this had been a “very important” development.

“We are talking about a potential systemic bank failure,” she told CNBC Wednesday.

— Reuters contributed to this report.