Global oil benchmark Brent crude fell $1 a barrel after weaker-than-expected factory activity data out of China and on concerns that the world's top crude importer's widening COVID-19 curbs will curtail demand.
Also weighing on prices, especially West Texas Intermediate crude futures (WTI), U.S. oil output climbed to nearly 12 million barrels per day in August, its highest since the onset of the COVID-19 pandemic, monthly government data showed.
Brent crude futures dropped $1.09 cents, or 1.1%, to $94.68 a barrel by 1240 p.m. (1640 GMT), extending Friday's 1.2% decline. WTI was down $1.98 cents, or 2.2%, at $85.98.
Both benchmarks, however, are on track for their first monthly gains since May.
Factory activity in China, the world's largest crude importer, fell unexpectedly in October, an official survey showed on Monday, weighed down by softening global demand and strict COVID-19 restrictions that hit production.
"The purchasing managers' index (PMI) data contracting adds to the post-China congress party blues for oil markets. It is not difficult to draw a straight line from weaker PMIs to China's COVID-zero policy," said Stephen Innes, managing partner of SPI Asset Management.
"So long as COVID-zero remains entrenched, it will continue to thwart oil bulls."
Chinese cities are stepping up zero-COVID curbs as outbreaks widen, dampening hopes of a rebound in demand.
Strict COVID-19 curbs in China have hit economic and business activity, curtailing oil demand. China's crude oil imports for the first three quarters of the year fell 4.3% year on year for the first annual decline for the period since at least 2014.
Meanwhile, the euro zone is likely to be entering recession, with its October business activity contracting at the fastest in nearly two years, a S&P Global survey said, as rising costs of living keeps consumers cautious and hurts demand.
European Central Bank policymakers are also standing behind plans to keep raising interest rates, even if it pushes the bloc into recession and stirs political resentment.
The Organization of the Petroleum Exporting Countries (OPEC) on Monday raised its forecast for medium and long-term oil demand and said $12.1 trillion of investment is needed to meet this demand despite the energy transition.
