In London, Brent North Sea crude for August delivery jumped 67 cents to 71.19 dollars per barrel in electronic deals.

New York's main oil futures contract, light sweet crude for delivery in August, gained 63 cents to 70.20 dollars.

On Thursday, New York crude struck 70.52 dollars -- the highest level since August 28, 2006.

Analysts said worries about tight US energy supplies were supporting prices.

"With US refineries starting to come back on line, US crude oil stocks will draw (fall)," Petromatrix analyst Olivier Jakobs said.

Crude prices had closed more than a dollar higher on Wednesday after the US Department of Energy (DoE) reported that American gasoline (petrol) stockpiles fell by 700,000 barrels to 202.6 million barrels in the week ending June 22.

That surprised the market, as analysts had expected a gain of 1.0 million barrels.

Gasoline reserves are in focus because of the US summer driving season when demand typically peaks as many Americans take to the roads for their annual vacations.

US gasoline inventories are running well below the lower end of the average range for this time of year, the DoE added in its weekly market update.

World oil prices had begun the week lower, as traders expressed relief at the end of a general strike in Nigeria that had threatened exports from the sixth-biggest crude producer in the world.