By Christian Berthelsen And Georgi Kantchev 

Oil prices rose Friday as traders anticipated another reduction in U.S. drilling activity and a survey said OPEC output fell in February.

Light, sweet crude for front-month April delivery was up 83 cents, or 1.7%, to $49.00 a barrel on the New York Mercantile Exchange, rebounding from Thursday's four-week low. The Brent crude contract was up $1.35, or 2.3%, at $61.40 a barrel on the ICE Futures Europe exchange.

The oil markets have been whipsawing in recent weeks with investors weighing signs of impending supply cuts and improving demand against indications of continuing global oversupply. The market has arrested the steep fall that prevailed from June to late January but remains volatile as traders assess whether the market rout is over. Brent, the global price benchmark, is up more than 13% in February while U.S. crude is broadly flat for the month.

Analysts caution the relative stabilization in the market masks weakness, with the global oversupply of oil continuing to grow and demand coming from temporary factors such as storing for later sale at a higher price rather than real-world use.

"The recent strength in oil prices is likely temporary and hides huge uncertainties with respect to the fundamental balance of the market," Barclays said in a note. Even accounting for the recent falloff in production from Libya, the bank estimated the glut would continue to grow at a pace of 1.2 million to 1.3 million barrels a day.

Still, there are some emerging signs of stabilization. A Reuters survey of shipping data and oil companies found that oil output from the Organization of the Petroleum Exporting Countries fell in February, as bad weather in southern Iraq delayed tanker loadings and sailings. The estimated output of 29.92 million barrels a day was lower than the cartel's official target of 30 million barrels a day and the lowest level since last June, when the market collapse began.

Oil prices might still drift lower in the short term as supply-side support to prices wanes in the weeks to come, JBC Energy said.

"Iraqi shipments for March should see a considerable lift as several February cargoes are deferred into March with plenty of vessels already in place to haul the crude. In the same vein, basically all onshore production in Libya was shut in following the sabotage of a key pipeline. Thus, it seems likely that any potential production and export volume changes will be to the upside," analysts at JBC wrote in a note.

The latest U.S. rig-count data will be released by oil-field-services firm Baker Hughes Inc. later on Friday. Investors in recent months have been fixated on the number as an indication of eventual supply cuts. The number of rigs drilling for oil has fallen by more than 35% since October.

Analysts, however, caution that a reduction in the number of U.S. oil rigs in use doesn't immediately translate to a fall in output, which is currently running at a multiyear high of 9.3 million barrels a day.

A weaker U.S. dollar on Friday was supportive of oil prices, traders said. As oil is priced in dollars, it becomes more attractive to holders of foreign currencies when the greenback depreciates. The Wall Street Journal Dollar Index, which tracks the dollar against a basket of currencies, fell 0.1% on Friday after rallying the previous day.

The premium of Brent crude prices to Nymex oil is at its widest in more than a year at $12 a barrel, on the back of increasing U.S. inventories, currently at an 80-year high for this time of the year.

China's official manufacturing PMI number is expected over the weekend, and market observers expect it to stay below the threshold of 50, indicating contraction. The data could have ripple effects in the market next week, as China is the world's second-largest oil consumer after the U.S. and a key driver of demand growth.

March gasoline futures rose 3.72 cents, or 2.2%, to $1.7448 a gallon on the Nymex. March diesel futures rose 8.72 cents, or 4.1%, to $2.2230 a gallon. The contracts expire with the end of trading Friday.

Write to Christian Berthelsen at christian.berthelsen @wsj.com and Georgi Kantchev at georgi.kantchev@wsj.com

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