U.S. oil rallied on Monday, rebounding from a five-year low, as data suggested that tumbling prices may have started to affect drilling activity in the fast-growing U.S. shale oil industry.
U.S. crude settled up $2.85, or 4.3 percent, at $69.00 a barrel, posting its largest daily gain since August 2012. The contract slipped to an intraday low of $63.72, the lowest since July 2009, earlier.
Benchmark was last up about $2 near $72 per barrel. It had fallen by almost $3 earlier to shy of $64, a low since July 2009.
A weaker dollar, which makes commodities denominated in the greenback more affordable to holders of other currencies, also enticed buying in oil and other natural resource markets, traders said.
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"There's a sense that the market got a little bit ahead of itself, and we're seeing some producer buying come in and it's driving the market back up," said Phil Flynn, analyst at the Price Futures Group in Chicago.
"I wouldn't be surprised to see it rally a couple more dollars. But I also wouldn't be surprised to see it sell back later in the session because of the volatile nature of things now and the perception among some that nothing has really changed fundamentally."
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Oil is still down about 10 percent since producer group OPEC's decision last Thursday not to cut output despite fears of a supply glut. Both Brent and U.S. crude have fallen for five months in a row, marking the longest losing streak in oil since the 2008/2009 financial crisis.
Saudi Arabia, the most influential member of the Organization of the Petroleum Exporting Countries, blocked moves by some smaller producers to curb output. The Saudis argued low prices would ultimately hurt U.S. shale oil production, which analysts say is responsible much of the oversupply now.
Data reviewed by Reuters on Monday suggested the new low-price environment for oil might have started affecting U.S. shale production, with a 15 percent drop in permits issued for new shale wells in October.
"The market is still looking for a new equilibrium below $70 (a barrel), which is a little surprising given that with the current prices, much of the shale oil production in the U.S., or part of it, will be unprofitable," Commerzbank analyst Eugen Weinberg said.
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With oil prices losing about 40 percent since June, the impact is felt around the world as oil-producers from Iraq to Nigeria are revising 2015 budgets to reflect lower prices.
Iran refrained from protesting against OPEC's decision to retain its production ceiling to maintain group solidarity, even though the move will not benefit all members, Iran's oil minister said in local media reports.
CNBC contributed to this report.