By early afternoon in Europe, benchmark oil for November delivery was up 94 cents to $90.92 a barrel in electronic trading on the New York Mercantile Exchange. The contract fell $1.39 to finish at $89.98 per barrel on the Nymex on Wednesday.
In London, Brent crude rose 97 cents to $111.01 per barrel on the ICE Futures exchange.
Victor Shum, an energy analyst at consultancy Purvin & Gertz in Singapore, said harsh rhetoric over Iran's nuclear program and threats by Israel of military action against Iranian nuclear installations renewed worries about oil supplies should an all-out conflagration erupt.
President Barack Obama told the U.N. General Assembly earlier this week that he wants to resolve the dispute through diplomacy but that the time to do so is "not unlimited." Obama also said the Iranian government has failed to demonstrate that its nuclear program is peaceful.
"Some of the comments from President Obama have caused some buying, causing oil to stabilize at around $90," Shum said.
The market gains started earlier, in Asia, helped by expectations the People's Bank of China will soon take more steps to stimulate the world's No. 2 economy, which is slowing down. The country is a big consumer of energy for its manufacturing sector.
Other Nymex energy futures prices:
— Heating oil added 1.15 cents to $3.114 per gallon.
— Wholesale gasoline rose 3.11 cents to $2.9049 per gallon.
— Natural gas rose 3.6 cents to $3.251 per 1,000 cubic feet.
Pamela Sampson in Bangkok contributed to this report.