US crude oil prices continued to fall Monday, diving below $40 a barrel to their lowest level since 2009, amid a global market selloff sparked by fears of China's slowdown.

US benchmark West Texas Intermediate (WTI) for October delivery tumbled by $1.39 to $39.06 a barrel on the New York Mercantile Exchange around 1305 GMT. On Friday the contract had slipped below $40 in intraday trade.