Benchmark global oil prices fell on Monday after a powerful North Korean nuclear test triggered a shift away from crude markets to assets perceived to be safer, such as gold.
Brent crude futures, the international benchmark for oil prices, were down 68 cents, or 1.3 percent, at $52.07 a barrel by 0808 GMT.
U.S. West Texas Intermediate (WTI) crude futures were more stable, down 8 cents at $47.21 barrel, as several refineries in the U.S. Gulf Coast restarted 10 days after Hurricane Harvey struck the region, boosting the outlook for demand in the world's top oil consumer.
Traders were nervously eyeing developments in North Korea, where the military conducted its sixth and most powerful nuclear test over the weekend.
Pyongyang said it had tested an advanced hydrogen bomb for a long-range missile, prompting the threat of a "massive" military response from the United States if it or its allies were threatened.