Crude oil was mixed on Friday, but Brent was set for its biggest monthly gain since August, as prolonged unrest in Libya kept supply disruptions in focus.
More than 40 people were killed in an explosion at an army depot in southern Libya after locals tried to steal ammunition, the latest in a series of clashes highlighting the government's inability to restore order. But steady progress in settling the dispute over Iran's nuclear program has kept gains in check.
Brent crude gave back early gains, trading down $1 under $110. U.S. oil, ended the session up 42 cents at $92.72. In a month of seesaw trading, the contract lost 2.2 percent this week, and 3.8 percent during the entire month of November.
Libya's oil exports are down to a fraction of capacity due to seizures of oilfields and ports by militias, tribesmen and civil servants demanding more political rights or higher pay. U.S. crude output last week exceeded 8 million barrels per day for the first time since January 1989, according to the U.S. Energy Information Administration.
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