Brent futures were down 45 cents, or 0.4%, at $108.33 a barrel, while U.S. West Texas Intermediate futures were off 69 cents, or 0.7%, at $103.56 a barrel at 0354 GMT.
Both contracts on Wednesday had shrugged off a large build in U.S. crude inventories to end the trading session roughly 4% higher.
"Demand growth is starting to moderate and the picture for the latter half of the year is looking increasingly bleak," said Vandana Hari, founder of oil market analysis provider Vanda Insights.
However, the oil complex is heavily focused on the short term and fears of supply shortages are crowding out that view, she said.
The International Energy Agency on Wednesday warned that from May onwards roughly 3 million barrels per day of Russian oil could be shut-in due to sanctions or voluntary embargoes.
The probability of a EU ban on Russian oil being agreed may be almost zero, but no one will be able or wanting to say that clearly, Hari said.
"And, even a continuing sabre-rattling will be enough to keep the risk premium alive."
At the same time, major global trading houses are also planning to curtail crude and fuel purchases from Russia's state-controlled oil companies in May, Reuters reported on Wednesday.
Despite signals that global supply disruption will persist, oil stocks in the U.S. rose by more than 9 million barrels last week, the U.S. Energy Information Administration said on Wednesday, driven in part by releases from the nation's strategic reserves. Analysts in a Reuters poll had anticipated just an 863,000-barrel build.
U.S. gasoline stocks fell 3.6 million barrels last week, far above anticipated levels, and distillate inventories also declined.
"Oil prices are looking very comfortable above the $100 level as U.S. and Chinese demand seems to be heading in the right direction," wrote Edward Moya, a senior analyst with OANDA.
