MOSCOW--The Russian ruble continued its advance in early trade Thursday, hitting levels last seen in late December.

The ruble has been in recovery mode for more than two months but its strengthening accelerated recently as demand waned for dollars and euros needed to repay debt. Households also started selling hard currencies they bought in late 2014.

The ruble gained 2% to 52.56 versus the dollar as of 0826 GMT, its strongest since Dec. 25. Versus the euro, the ruble firmed by 2.4% to 56.45, a level last seen on Nov. 25.

The once-battered Russian currency is enjoying inflows thanks to the central bank's key rate of 14%, which is far above dollar and euro rates and so offers an opportunity for carry trade. With prices for oil--Russia's key export--stabilizing close to $60 per barrel, some players are closing their short positions on the ruble.

"We stick with our view that technical factors are currently playing the key role in the forex market as mainly international accounts cover their dollar/ruble longs opened weeks before around 60.0 levels," VTB Capital said in a note.

"Predicting to what point that activity could take the market would be walking on thin ice, given relatively low liquidity on the bid, since imports remain subdued, while the peak of external debt payments has passed in the first quarter," VTB said.

Month-end taxes, which kick in next week, may provide additional support for the ruble. But the more the ruble recovers, the greater the risks that it may depreciate again if news flow turns negative, ING Bank said in a research note.

Write to Andrey Ostroukh at andrey.ostroukh@wsj.com