Crude oil prices were down at trading start on Tuesday with investor concerns that China's weak manufacturing data would weaken oil demand from the world's second largest consumer.
International benchmark Brent crude was trading at $71.33 per barrel at 0650 GMT, posting a 0.2% loss, after it closed Monday at $71.48 a barrel.
American benchmark West Texas Intermediate cost $63.38 a barrel at the same time for a 0.3% decline, after ending the previous session at $63.55 per barrel.
China's manufacturing sector showed weakness in April, compared to the month before, indicating that crude oil demand from the country could decline over the coming months putting a downward pressure on oil prices.
Purchasing Managers' Index (PMI) in China fell to 50.1 in April, from 50.5 in March but managed to remain just above 50 to avoid contraction, according to the country's National Bureau of Statistics data released earlier.
China's non-manufacturing PMI declined to 54.3 in April, from 54.8 the previous month, according to the data.
After contracting for five consecutive months, China's manufacturing industry returned to growth in March supported by the government' stimulus steps.
A PMI higher than 50 indicates the expansion of the sector, while lower than 50 shows a contraction, and 50 points reflects no change.
By Ovunc Kutlu