Asian shares slid to their lowest levels since late 2011 on Monday after weak U.S. economic data and massive falls in oil prices stoked further worries about a global economic downturn. Oil prices fell as much as 4 percent on Monday, with international benchmark Brent futures (LCOc1) falling below $28 per barrel (LCOc1), touching their lowest level since 2003. In China, the Shanghai Composite index (.SSEC) fell nearly 2 percent, piercing through intraday lows last seen in August when China’s markets nosedived.