Brent crude futures have fallen below $100 per barrel during Friday's trades, for the first time since October 2011.
Brent for July settlement fell to $99.61 a barrel on mid-Friday, the lowest level since October 4 when it stood at $99.11, before nudging back over $100. As of 13:40 Moscow time it was at $100.22.
Investor sentiment was undermined by the European Purchasing Managers' Index fell 0.8 to 45.1 points in May from the previous month.
The PMI, a composite indicator of the manufacturing economy, signals growth when above 50 points and contraction when below, flagging continuing weak crude demand in Russia’s largest trade partner.
Also clouding the economic horizon was a weak PMI figure from China, which posted a May reading of 50.4, its weakest in five months.
The oil price slump has been a factor behind the ruble’s depreciation against major world currencies. As of 14:08 p.m. Moscow time (10:08 GMT), the ruble lost 46 kopecks against the greenback to 33.94 rubles to the dollar, near the psychologically important level of 34 rubles to the dollar, and plunged 40 kopecks against the euro to 41.82.
On the Russian stock market, the ruble-denominated MICEX had fallen 0.81 percent to 1,295.85 points by 14:22 p.m. Moscow time, while the dollar-denominated RTS was down 2.14 percent to 1,215.93.