When they took out a mortgage on a small two-room apartment seven years ago, Oksana Li and her husband hoped to make a new home for themselves and their young son.

Now, like thousands of other Russians, they are seeing that dream unravel as they are unable to make payments - even by working longer hours and a second job.

That is because they are part of a minority of Russians who took out mortgages denominated in a foreign currency to take advantage of lower interest rates abroad. As Russia's currency collapsed in recent months, the cost of repaying those mortgages has gone through the roof.