NEW YORK—Oil prices plunged to fresh six-year lows Monday, as sharp declines in Chinese equities fueled concerns about global economic growth.

Brent, the global oil benchmark, fell through its January lows to trade below $45 a barrel for the first time in six years. Brent recently fell $2.36, or 5.2%, to $43.10 a barrel on ICE Futures Europe, the lowest intraday levels since March 2009.

The U.S. oil benchmark recently traded down $2.02, or 5%, to $38.43 a barrel on the New York Mercantile Exchange, the lowest intraday price since February 2009.

The falls in crude followed an 8.5% decline on the Shanghai Composite Index, the biggest percentage decline since 2007. China is the world's largest consumer of commodities, and second-largest consumer of oil after the U.S.

Concerns about a slowdown in Chinese economic growth have roiled global financial markets. U.S. and European stocks dropped sharply Monday, and Treasurys gained.