Light, sweet crude for February delivery rose $2.56 to $40.27 a barrel in electronic trading on the New York Mercantile Exchange by midday in Europe. The contract on Friday rose $2.36 to settle at $37.71.
Israel expanded its deadliest-ever air offensive against Gaza's Hamas rulers Sunday and prepared for a possible ground invasion. Arab leaders protested the attacks and Syria broke off indirect peace talks with the Jewish state.
With the two-day death toll nearing 300, Hamas fired rockets deeper than ever into Israel.
"There could be fear that an escalating Middle East conflict could disrupt supplies, though I don't see that happening at this point," said Gerard Rigby, energy analyst with Fuel First Consulting in Sydney. "(Israel-Palestinian conflict) always causes a bit of a blip and is one component that could support prices short-term."
In Vienna, JBC Energy, in its daily newsletter, said prices were also "supported by news that the UAE has decided to reduce crude supplies in January and February in line with the OPEC production cuts." The United Arab Emirates are the fourth-largest producers in the 13-nation cartel.
But any recovery could have its limits.
Oil prices have fallen 73 percent since peaking at $147.27 a barrel on July 11 as a credit crisis in the U.S. sparked a steep drop-off in consumer demand and corporate earnings. And analysts expect more dismal economic news from the fourth quarter over the next few weeks.
"More bad profit reports, jobs reports, housing results will put pressure on prices," Rigby said. "Once Obama comes in, that might start changing sentiment and generate more optimism." Barack Obama is scheduled to be sworn in as U.S. president on Jan. 20.
Trading volumes have been low as many traders take off the week between Christmas and New Year's Day.
In other Nymex trading, gasoline futures gained more than 7 cents to 92 cents a gallon. Heating oil rose by close to 10 cents to fetch 3.30 cents to $1.34 a gallon, while natural gas for January delivery jumped more than 14 cents to $5.97 per 1,000 cubic feet.
In London, February Brent crude rose $2.98 to $41.35 a barrel on the ICE Futures exchange.
Associated Press writer Alex Kennedy contributed to this article from Singapore.
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