Barclays Capital said investors withdrew $8.2 billion from commodity investments in May, the largest in eight months.
"A 'perfect storm' of downgrades, lackluster macroeconomic data and the ongoing eurozone debt crisis transformed a retreat by investors into something approaching a stampede during May, evoking memories of 2008," Barclays said in a research report.
Barclays said May ended with total assets under management of $394 billion in commodities, down $35 billion from the previous month.
"The speed and extent of recent commodity price falls suggest market participants are anticipating a severe deterioration in the macroeconomic outlook," the bank said.
Energy saw the largest outflows in May, at $2.7 billion, the highest since December last year. Agriculture saw the second-biggest outflow at $2.3 billion, the highest since September last year.
For precious metals, outflows of $1.9 billion were the highest in exactly a year, the bank said.
"Commodity data flow is still healthy, and if the green shoots of recovery in China take root, a mild recovery in prices is likely. However, longer-term gains will likely remain capped by European leaders failing to enact a lasting solution to the crisis.
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