A measure of financial shares was the biggest drag among the MSCI benchmark's 10 industry groups.
Samsung Electronics Co, Asia's largest maker of flat panels, chip and mobile phones, declined 4.7 percent to 584,000 won.
LG.Philips LCD Co, the second-biggest maker of liquid-crystal displays in the world, slipped 1.1 percent to 40,400 won.
South Korea resumed trading after a three-day holiday during which the MSCI Asia Pacific Index, which includes Japan, dropped 4.2 percent after a surprise contraction in US service industries fueled concern that the world's largest economy is in a recession.
A separate US report showed pending home sales dropped to the second-lowest level since the National Association of Realtors began keeping records in 2001.
"There's no doubt that slower growth in the US will cut growth in other parts of the world," said Troy Angus, who helps manage the equivalent of US$3.5 billion at Paradice Investment Management Ltd in Sydney.
Reliance Power plunged 13 percent to 391.5 rupees, after earlier slumping as much as 14 percent. The unit of Reliance Energy Ltd, India's second-biggest utility by market value, sold its stock at 450 rupees in an initial offering. Investors ordered shares valued at as much as US$189 billion.
Reliance Energy tumbled 16 percent to 1,650 rupees.
Ansell Ltd, the biggest maker of surgical gloves in the world, jumped 3.5 percent to A$11.90 after saying that its first-half profit increased 28 percent.
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