Berni Moestafa – Indonesia's stocks fell, with the benchmark index set for its biggest loss in almost a year, on concern a global economic recovery is slowing, reducing demand for the nation's commodities.

The Jakarta Composite index plunged 4.4 percent to 2,252.95 as of 10:15 a.m. local time, on course for its steepest decline since Nov. 13. The gauge was the biggest decliner in Asia.

The rupiah also fell, set for its longest slump since April, as investors continued to scale back positions in emerging markets and high-risk currencies.

"People are just panicking," said Finny Fauzana, a fund manager at PT PNM Investment Management, which manages about $145 million in assets in Jakarta. "If the global economic outlook remains weak or the recovery isn't going as well as thought, then that will put a cap on our commodity prices."

PT Bumi Resources, Indonesia's biggest coal producer, slumped 8.3 percent to 2,200 rupiah. PT International Nickel Indonesia plunged 6.3 percent to 3,700 rupiah. Energy and mining shares are the biggest losers among the market's nine industry groups.