Stock markets world-wide tumbled on Friday, Brent crude oil prices fell to seven-year lows and China's yuan currency sank on risk aversion ahead of a widely anticipated US interest rate increase next week and worries over economic growth. All three major US indexes sank over 1.5 percent, while crude prices plunged amid global oversupply. The International Energy Agency said it sees the oil glut worsening in 2016 as demand slows and Opec shows no signs of slowing production. Brent crude was set for its biggest weekly percentage drop in over a year and US crude was set for its biggest percentage decline in roughly a year. China's yuan fell to its lowest in four-and-a half years on concerns over a slowdown of the world's second-biggest economy and expectations of a US rate hike. Concerns grew that weakness in the yuan could weigh on the global economy and on companies with strong export ties to China. "We have the yuan at 4-1/2 year lows and that is causing unease in China and abroad," said Jasper Lawler, market analyst at CMC, said. In the spot market, the yuan hit 6.4564 against the US dollar, its weakest level since July 2011. Brent crude was down 4.48 percent at $37.95 a barrel after hitting $37.36, its lowest since December 2008. US crude dropped 2.86 percent to $35.71 per barrel after hitting $35.35, its lowest since February 2009. On Wall Street, the three major stock indexes were on track for their worst weekly drop in a month. The Dow Jones industrial average was down 1.55 percent, to 17,302.09. The S&P 500 was down 1.67 percent, at 2,018.05. The Nasdaq Composite was off 1.85 percent, at 4,951.92. European shares slipped to their lowest in two months, with a measure of top regional shares posting its biggest weekly drop in three and a half months. Europe's broad FTSEurofirst 300 index ended 2.14 percent lower at 1,397.49. MSCI's all-country world equity index, which tracks shares in 45 nations, was down 1.44 percent at 393.61. The dollar fell against the euro as concerns over weak commodity prices and the yuan's slump overshadowed solid US retail sales data. Those concerns were unsupportive of further monetary policy tightening by the Fed beyond December's heavily anticipated rate increase.