Oil firmed above $61 on Friday as support came from crude fundamentals in leading consumers China and the United States, and Africa's top producer Nigeria, along with further signs of economic resilience.
U.S. crude futures were up 52 cents at $61.57 a barrel by 7:46 a.m. EDT. It hit a six-month high of $62.26 this week.
London Brent was trading 52 cents higher at $60.55.
Oil has recovered from a five-year low below $33 in December, having plunged from record highs above $147 last July.
U.S. investment bank Goldman Sachs said the hike in prices this week was due to real oil market fundamentals and not just hedging against a weak dollar and equity market rallies.
"The oil market was shocked by disruptions in Nigeria, refinery problems in the U.S. and a strong gasoline market," Goldman said in a research note.
The Nigerian military has launched its biggest campaign for years in the country's oil heartland, bombarding militant camps, which has sent shockwaves and fears of further supply disruptions from the West African country through oil markets.
Goldman said recent refinery fire and outages in the world's top consumer, the United States, had also unnerved markets.
The refinery problems pushed up gasoline prices ahead of the Memorial Day holiday this weekend, which marks the start of the traditional U.S. driving season until July.
Support also came from China, the world's second-largest energy consumer. Data on Friday showed China's apparent oil demand rose by 3.9 percent in April from a year earlier, its first significant rise since October last year.
Oil traders were expected to shift their focus to next week when the Organization of the Petroleum Exporting Countries will meet to review its output policy on Thursday.
OPEC is expected to keep its official production levels unchanged as rising prices have eased pressure on budgets and there are hints of economic recovery over the next year, a Reuters poll showed on Thursday.
Contraction in world economic output appeared to be slowing and a recovery could begin at the end of this year, Organization for Economic Development and Cooperation (OECD) said on Friday.
OECD's chief Angel Gurria said at an economic forum that indicators ranging from U.S. house sales to Chinese exports were beginning to pick up and the global economy was no longer in free fall.
