Brent oil climbed above $67 today after Nigeria's elections drew condemnation and investors waited for word on oil supplies from the world's eighth biggest exporter.
Militant attacks have shut about a fifth of Nigeria's oil production. Energy Minister Edmund Daukoru said last week he expected the country's biggest foreign operator, Royal Dutch Shell, to restart its Forcados fields in May.
US crude was up 31 cents at $64.42. Ruling party candidate Umaru Yar'Adua looked set to win Nigeria's presidential poll, early results showed, but monitors condemned the vote as a blow to the progress of democracy in the country.
International and local observers said the ballot for the first handover of power from one civilian leader to another was compromised by ballot-stuffing, violence and a shortage of millions of voting papers.
About 500,000 barrels per day of Nigerian oil output has been shut down for over a year due to attacks on oil installations and at least 50 people died in violence surrounding Nigerian state polls earlier this month.
Analysts also said tight petrol supplies in the United States ahead of the summer driving season presented an upside risk.