Oil prices fell back close to $40 a barrel this evening, having begun the day higher, at the end of a very volatile week. US crude fell $1.35 to $40.35 a barrel, while Brent North Sea crude shed 96 cents to $43.71.
Oil prices had fallen on Thursday on concerns over a build up of US stockpiles and worries that the global economic slump would further dampen demand.
The US Department of Energy said on Wednesday that stockpiles of crude increased 6.7 million barrels last week, far higher than predictions from analysts for a gain of only 700,000 barrels.
Oil prices rallied at the start of the week, bouncing back above $50 in London as the market was shaken by disruptions to gas supplies across Europe, already troubled by a cold snap.
Russia has cut supplies bound for Europe via Ukraine in retaliation for Ukraine's alleged theft of Russian gas. Ukraine denies siphoning off Russian gas and has accused Moscow of engineering the crisis but by Friday the dispute appeared to be nearing a resolution.
