KYIV - Russian lender Sberbank said Monday it was deeply concerned by protests against its Ukrainian subsidiary, which included a nationalist group walling up the entrance to one of its branches in Kyiv with masonry and cement.

Periodic protests have been held against Kremlin-owned banks operating in Ukraine since bilateral ties broke down in 2014 after Russia annexed Crimea and gave its support to the pro-Russian separatists in eastern Ukraine.

Sberbank's announcement last Tuesday that it would heed a call from President Vladimir Putin to recognize passports issued by separatists in eastern Ukraine has fueled greater discontent.

On Monday, a few dozen members of a new activist group called National Corp blocked off the entrance to Sberbank's main branch in central Kyiv. The branch temporarily suspended operations and appealed to the police.

"Sberbank is highly concerned about the situation in Ukraine linked to the actions of representatives of nationalist groups," the bank said in a statement. "Our subsidiary has already appealed to law enforcement bodies and we hope that all necessary steps will be swiftly taken to ensure the safety of our workers and clients and protect property."

It said over the past week it had recorded over 26 acts of vandalism against Sberbank Ukraine's branches and bank machines.

Last week, the central bank said it could recommend the introduction of sanctions on Sberbank's subsidiary for its recognition of separatists' identity documents.

Five Russian state-owned banks are present in Ukraine, including three in the top 20, and they hold a combined market share of 8.6 percent.

The central bank has been seeking to cut that following the souring of relations between the one-time allies.

It is not yet clear how the other Kremlin-owned banks operating in Ukraine are handling Putin's order to recognize separatist documents.