Russian borrowers will need to figure out how they're going to pay about US$9 billion over the next three months.

That's the approximate amount of cash that Russia's companies and government are due to pay holders of foreign-currency bonds before the end of May, according to data compiled by Bloomberg. That task has been complicated by the swath of international sanctions that have been imposed on Russia following its invasion of Ukraine, as well as President Vladimir Putin's response: capital controls, albeit ones that are set to exclude the need to service existing debt.

"Accessing dollar liquidity could be difficult," said Timothy Ash, senior emerging-market sovereign strategist at BlueBay Asset Management in London. "Technically it might be difficult to pay" due to platforms that typically facilitate transactions closing access to Russia, he said.