Oil prices for benchmark WTI and Brent crude fell on Monday as stock markets suffer heavy losses and global markets slow down, reported Reuters.

WTI Crude—the US measure for light, sweet crude oil—was under $40 on markets, the lowest in six years. London’s Brent Crude index had an even sharper percentage drop, at 6% in one day.

Many analysts blame the steep drop off to a slowing China. “Today’s falls are not about oil market fundamentals. It’s all about China,” Carsten Fritsch, senior oil analyst at Commerzbank in Frankfurt, told Reuters Global Oil Forum. “The fear is of a hard landing and that things get out of the control of the Chinese authorities.”

Adding to the problem are oil producers refusing to cut production, the Wall Street Journal noted. The principal figures are US shale drillers and OPEC countries, with both vowing not to cut production. Fears of Iran adding oil to the already over-supplied market are driving prices down even further.

Yesterday Chinese markets experienced the steepest single-day drop yet, with nearly $500b wiped off the FTSE Eurofirst 300 value.

US WTI’s index is down 18% this month, with Brent following at 16%