Russia's central bank agreed has agreed to rescue B&N Bank by injecting extra capital, becoming the main investor in the troubled lender and its affiliated banks. 

B&N Bank is Russia's 12th biggest lender by assets.

It said yesterday it had requested a rescue because problem assets on its books were too great for it to handle. 

The second major Russian bank bailout in a month has raised fresh questions about supervision and the stability of a banking sector buffeted by an economic downturn and Western sanctions. 

Russia's central bank said in a statement it will use money from its Fund for the Consolidation of the Banking Sector to improve B&N Bank's financial stability. 

"It is planned that the Bank of Russia will participate as the main investor," it said, adding that it would not use a so-called bail-in of B&N Bank's creditors for the rescue. 

The rescue package would apply to B&N Bank, affiliated lender Rost Bank, and other banks in the group, it said. 

"Implementation of measures to improve the financial stability of the banks is being carried out in co-operation with the current owners and managers of the banks, which will ensure their uninterrupted operation," it said. 

Russian banks were already under stress from an economic slowdown made worse by Western sanctions. They have seen bad debts rise over the past three years. 

The financial health of some worsened after the central bank forced them to make more rigorous provisions for non-performing loans, while margins have tightened due to lower interest rates. 

The central bank took over Otkritie, Russia's largest private lender, last month and said it may need up to $6.9 billion, the biggest ever bailout in the country. 

The market sees the banking sector's problems as contained to a few mid-sized private banks which have problems not shared by the wider banking industry. 

Most of the Russian banking sector's assets are in the hands of state-run banks which are much more solid and not at immediate risk, analysts and market insiders said.