International Brent crude oil futures were at $67.63 a barrel at 0045 GMT, down 20 cents, or 0.3 per cent, from their last close. Brent closed down 0.2 per cent on Wednesday.
US West Texas Intermediate (WTI) crude futures were at $59.18 per barrel, down 23 cents, or 0.4 per cent, from their last settlement. WTI fell 0.9 per cent on Wednesday.
Prices came under pressure from a rise in US inventories, although analysts pointed to support from efforts by the Organization of the Petroleum Exporting Countries (OPEC) and non-affiliated allies like Russia, known as OPEC+, to trim output.
"Today's fall does not derail the short-term bullish argument that both the OPEC+ production cuts and supply outages will outweigh the global growth concerns and rising US production," said Edward Moya, senior market analyst, OANDA.
US crude inventories rose last week by 2.8 million barrels, compared with analysts' expectations for a decrease of 1.2 million barrels, the US Energy Information Administration said.
Crude exports fell by 506,000 barrels per day, the EIA said.
Offering support for prices, oil output from Russia, OPEC's biggest non-member ally, averaged 11.3 million barrels per day so far in March, a source said, compared with 11.34 million barrels a day the previous month.