Oil climbed towards $63 a barrel on Thursday, supported by refinery closures that are cutting gasoline supplies in top consumer the United States just ahead of the summer driving season.
U.S. crude futures rose 41 cents on Thursday, while London Brent crude rose 69 cents.
"There's still a relatively low rate of refinery runs -- the current tightness in gasoline is unlikely to ease in the short term," said Makoto Takeda, analyst at Bansei Securities.
Despite record pump prices above $3 a gallon, U.S. demand remained robust, he said, adding that inventories were still at the low end of their five-year range.
Refinery shutdowns in the United States have kept worries bubbling over a summer supply crunch, with investors drawing little comfort from a surge of gasoline imports.
Gasoline stocks rose 1.7 million barrels last week after imports rose to 1.5 million barrels per day (bpd) -- the fifth highest level on record.
The U.S. inventory figures on Wednesday had added to pressure on prices after the end to an occupation of an oil hub by Nigerian villagers that had forced operator Royal Dutch Shell to cut output by 170,000 bpd.
Militant attacks have shut nearly 900,000 bpd, or 30% of supply capacity, from Africa's biggest oil producer -- depriving refiners of crude prized for its gasoline content.
The Nigerian disruptions, together with worries over Iran's dispute with the West and supply cuts by OPEC producers, have pushed crude well above a January low near $50.
Consumer nations have called on OPEC to open the taps, but the group that supplies a third of the world's oil says it sees no need to act. Its next scheduled meeting is in September.
"OPEC is incredibly relaxed at the current state of the market," said Barclays Capital. "Without that increase, we expect the market to overheat in the second half of the year."
Abdullah al-Badri, the group's Secretary-General, said OPEC is content with prices in their current range.
"I don't want to see a low price and I don't want to see a high price," he said on Thursday.