Shares in mining and trading company Glencore fell almost 30% and closed at a record low on Monday over concerns it is not doing enough to cut its debt to withstand a prolonged fall in global metals prices.
Crude oil prices fell more than 2% on Friday after Goldman Sachs cut its crude forecasts, citing global oversupply and concerns over the Chinese economy, and after Saudi Arabia dismissed the idea of an oil producer summit.
Wall Street racked up its biggest one-day gain in four years on Wednesday as fears about China's economy gave way to bargain hunters emboldened by expectations the U.S. Federal Reserve might not raise interest rates next month.
Bitcoin is a virtual or online currency created through a "mining" process where a computer's resources are used to perform millions of calculations. Once mined, bitcoins can be stored in an online wallet, traded in an online exchange, or used to buy goods and services.