Ukraine and Western nations are accusing Russia of deliberately trying to destabilize parts of eastern Ukraine ahead of national elections in late May. Russia's foreign minister Sergey Lavrov has denied that Russian forces were active in the east.
Last month, Russia took control over Ukraine's Crimea region.
The central bank action to defend the economy came as Germany's RWE(RWEOY) said it was starting to pump natural gas to Ukraine via Poland.
Ukraine relies on Russian gas, but owes at least $2.2 billion in arrears. Last week, Russian President Vladimir Putin threatened to cut off gas exports to Ukraine.
"RWE believes that further significant volumes could be delivered to Ukraine if various transport restrictions at the Slovakian/Ukrainian border are politically and technically resolved within the next weeks or months," the company said in a statement.
Supplies from western Europe could ease the pressure on Kiev if Russia follows through with its threat.