The crisis has crept up in recent weeks amid wrangling by national fuel marketers over more than $1bn in alleged outstanding payments by the outgoing administration of President Goodluck Jonathan.

Nigeria earns 75% of its budget from oil. The country uses much of that revenue to subsidize fuel prices. Nigerians buy gasoline for just $1.65 a gallon. To the companies that sell fuel to Nigeria, the government pledges to pay the difference between that price and the market rate within 45 days.

OAO Rosneft may have to turn to competitors to buy natural gas and state aid to help honor a $50 billion contract it won away from OAO Novatek three years ago, according to two people with knowledge of the matter.

Millions of barrels of untapped oil that U.S. shale drillers discovered during the boom years are about to disappear from their inventories.

China's April imports of crude oil from Middle East suppliers rose 10% year on year to a record high of 16.61 million mt or 4.06 million b/d, led by Saudi Arabian supply, according to detailed data released Saturday by the General Administration of Customs.

“Geopolitical turmoil that takes foreign oil supplies offline can be difficult to predict or control, but the U.S. will always have control over how much energy we produce here at home. With the right policies, our energy renaissance can endure for decades and help even more families afford to take a vacation on Memorial Day weekend.”

BHI Rig Count: U.S. -3 to 885 rigs

Prices have also risen with internationally traded Brent recovering from a six-year low near $45 a barrel in January to $64.90 on Wednesday.

Crude oil prices bounced back on Wednesday from steep falls in the previous session as strong Japanese economic growth surprised markets and the business outlook in Australia also seemed to brighten, stoking producer hopes of increased demand.

U.S. economy is thought to have shrunk in the January-March quarter and may barely grow for the first half of 2015 — thanks in part to sharp cuts in energy drilling. And despite their savings at the gas pump, consumers have slowed rather than increased their spending.