Oil prices rose nearly $1 a barrel Friday ahead of the weekend presidential election in Nigeria, where gunmen attacked a boat carrying oil workers near the nation's southern oil region.
Traders also were positioning ahead of the May contract's expiration on Friday, which kept the June contract gains minimal.
The electoral period in Nigeria — Africa's largest oil producer and a main supplier to the United States — has been chaotic. At least 49 people have died in violence since April 14 and many more were reported dead in political violence before last weekend's state vote.
Officials said Friday that gunmen attacked a boat carrying oil workers to an offshore rig in waters off Nigeria's unruly south, wounding six, officials said. Security forces drove off the attackers, a private security official said.
Light, sweet crude for May delivery rose 97 cents to $62.80 a barrel in midday trading on the New York Mercantile Exchange. The June contract, which moves to the front month Monday, rose 39 cents to $63.71.
Brent crude for June rose 31 cents to $66.25 a barrel at London's ICE Futures exchange.
"With so many reasons for there to be short-covering ... it would be natural for prices to advance briskly on what everyone will say are fears over Nigeria's weekend election," said Peter Beutel of Cameron Hanover.
"If that happens, then this market still has the ability to rise on this type of news. And, since that ability correlates much more closely with bullish markets, price strength on Nigeria fears today could tell us we are still in a bullish market."
More than 150 foreigners have been kidnapped over the past year in Nigeria's southern region where crude is pumped in Africa's largest producer. Stepped-up violence has trimmed Nigeria's daily production by about one quarter, helping send global crude prices higher.
In other Nymex trading, heating oil futures rose 1.31 cent to $1.8189 a gallon, while natural gas dropped 11 cents to $7.382 per 1,000 cubic feet. Gasoline futures rose 1.72 cent to $2.1060 a gallon.
The price increases came after an abrupt drop the day before. The May contract tumbled more than $1 Thursday to a one-week low, settling at $61.83 a barrel, as traders focused on inventory buildups at a key Oklahoma oil terminal.
Also stoking inventory concerns was Enbridge Inc.'s announcement that it reopened a pipeline that had been closed due to a leak on Sunday. The line is used to move crude oil from Canada to the Midwest.
Prices were further weighed down by a consultant's report that
Iraq oil reserves could be much larger than initially expected, and reports that China may take more serious steps to slow its economic growth, thus using less oil. China's gross domestic product grew 11.1 percent in the first quarter.
Crude oil prices had slumped more than 6 percent since March 29, when they hit a six-month closing high as
Iran's capture of 15 U.K. marines and sailors raised fears of an armed conflict.
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