Crude prices fell to $103 a barrel on Monday weighed by a stronger dollar and a drop to an eight-month low in oil demand in the world's second-largest consumer China.
China's refinery crude throughput fell 3 percent in April from March, its lowest daily rate since last September, as refineries entered maintenance season. Implied oil demand was up 3.2 percent in April from a year earlier to about 9.6 million barrels per day (bpd), the lowest in eight months.
Brent crude slipped 80 cents to $103.11 barrel by 1200 GMT. U.S. oil fell 39 cents to $95.65 a barrel.
"The economic data in China is not yet providing upward support. It is not that it is weak, it is simply not sufficient to support a bullish trend," Harry Tchilinguririan, head of commodity market strategy at BNP Paribas, said.
A firm dollar, which makes oil more expensive for holders of other currencies, also kept a lid on prices.
The dollar has risen on speculation that the Federal Reserve could scale back its aggressive monetary stimulus aimed at supporting growth.
"The value of the dollar has weighed on the prices of all commodities, specially the more sensitive ones such as oil and gold," Tchilinguririan said.
News that oil flow through the Iraq-Turkey pipeline was halted on Monday shortly after its resumption following a 6-day stoppage offered some support.
The market remained bearish on the supply side, too.
"The oil market remains oversupplied, with U.S. crude oil stocks at a record level and gasoline stocks in the Amsterdam-Rotterdam-Antwerp (ARA) region riding at a five-year high," according to analysts at Commerzbank.
The International Energy Agency (IEA) will release its monthly supply and demand outlook on Tuesday after OPEC last week increased its outlook for 2013 demand.
"In the medium-term Oil Market Outlook it will be publishing tomorrow, the International Energy Agency (IEA) is likely to revise its forecast for non-OPEC oil supply significantly upwards to take account of the rapid growth of shale oil production in the U.S. Positive news about demand is therefore needed if oil prices are to climb," Commerzbank said.
Renewed worries of a slowdown in demand growth from the world's top oil consumer the United States also limited gains.
The U.S. economy is expected to grow at a slower pace in the second and third quarters of this year, according to the Philadelphia Federal Reserve's quarterly survey of 42 forecasters, compared with its previous estimates. (Additional reporting by Manash Goswami; Editing by William Hardy)