Volatility erupted anew in financial markets as a fresh year brought jarring swings, anxiety about global growth and the worst start on record for equities both in the U.S. and in the world.

European shares fell yesterday, with lingering worries about China causing a major regional equity index to suffer its worst weekly loss since August 2011.

U.S. stocks capped the worst week since September 2011 and crude tumbled to a 12-year low as the effects of China’s attempts to shore up financial markets faded. Treasuries posted the biggest weekly advance since October.

Standard & Poor’s 500 and Dow Jones Industrial Average fell by 6% and 6.2%, respectively, in the biggest ever fall for the first five days of January

Global equities capped their worst start to a year since 2000, with the Dow Jones Industrial Average sliding more than 250 points, as China unexpectedly weakening its currency fueled fresh concern over the strength of the world economy. Bonds gained.

Chinese stocks gained in volatile trading after the government suspended a controversial circuit breaker system, the central bank set a higher yuan fix and state- controlled funds were said to buy equities.