Oil prices declined on Monday, finishing the first session of the week at its lowest level in about three weeks.
A surge in new COVID-19 cases is raising concerns about demand and economic recovery, especially in the United States and Europe.
Brent crude futures for December delivery lost $1.31, or 3.1%, and closed at $40.46 per barrel.
Meanwhile, the West Texas Intermediate (WTI) crude futures for December delivery dropped by $1.29, or 3.2%, and settled at $38.56 per barrel.
This is the lowest closing level for the global and US benchmark crude oils since October 2.