Moscow (AFP) - Russia's battered ruble fell Thursday on the back of weaker oil prices to more than 75 to the euro for the first time in over six months, deepening its recent decline.

The ruble also tumbled against the dollar to near 67.44, its weakest against the greenback since February.

Russia's currency has fallen more than 20 percent against the dollar in the past two months, sparking fears of more instability after a period of relative recovery.

Russia's economy has slumped into recession amid lower oil prices and Western sanctions over the Ukraine crisis.

Oil prices slid to a new six and a half year low in Asia on Thursday, approaching the key $40 a barrel level after a surprise rise in US inventories added to concerns of a supply glut.

The ruble lost around half of its value in 2014 but recovered slightly as energy prices stabilised this year, allowing officials to claim the worst of the crisis had passed.

But the recent decline, resulting from a renewed fall in oil prices has highlighted how volatile the situation remains.

The recent slump has seen the central bank curb moves to cut back interest rates as it seeks to juggle renewed inflation fears against attempts to breathe life into the flagging economy.