Oil prices Monday extended last week’s steep slide, falling more than 4% in early trading, hitting their lowest level since May before trimming some of that decline.

The drop comes atop last week’s 6% slump, which marked the biggest weekly loss in four months.

Pressuring oil: concerns that new restrictions stemming from the spike in COVID-19 cases in Asia, especially China, could dent fuel demand.

China’s COVID-19 cases are just a fraction of that of the U.S., but they’re climbing quickly, and the sharp jump in new cases reported on Monday sparked worries. Add to that a report showing the country’s export growth slowed in July partly owing to outbreaks of COVID cases. Flight cancellations and other new travel restrictions imposed by China also exacerbated those concerns, as well as warnings by cities against travel and limits on public transport and taxi services in badly hit areas.

Crude oil is priced in U.S. dollars, so the greenback’s rally to a four-month high against the euro also weighed on oil prices. For holders of other currencies, a stronger dollar makes oil more expensive to buy.