Brent crude futures, which act as a benchmark for international oil prices, were at $71.59 per barrel at 0413 GMT, down 24 cents, or 0.3 percent, from their last close.
U.S. West Texas Intermediate (WTI) crude futures were down 24 cents, or 0.4 percent, at $65.67 per barrel.
Reuters technical commodity analyst Wang Tao said Brent and WTI would likely come under pressure soon, testing support at $70.62 per barrel and $64.83 per barrel respectively.
“Disappointing industrial data out of China along with concerns over emerging market economies centered on Turkey weighed on commodities,” Edward Bell of Emirates NBD bank said in a note on Sunday.
In the United States, U.S. energy companies last week kept the oil rig count unchanged at 869, according to the Baker Hughes energy services firm .
“The recent softening in benchmark prices should temper the pace of growth in U.S. exploration and production activity, and lead to slower overall output growth,” Bell said.
Outside the United States, traders said U.S. sanctions against Iran could soon impact prices.
The U.S. government has introduced financial sanctions against Iran which, from November, will also target the country’s petroleum sector.
Iran produced around 3.65 million barrels per day of crude in July, according to a Reuters survey, making it the third biggest producer within the Organization of the Petroleum Exporting Countries (OPEC), behind Saudi Arabia and Iraq.
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