``Shut down the stock exchange,'' the 50 union leaders shouted in front of the office of the head of the exchange in Seoul's Yoido district, a business and government center.
The union leaders said a temporary halt in trading would help ease what they called a catastrophic situation in the Korean stock market.
``It's unfair that all the burden of the bankrupt South Korean economy is being passed on to stock investors who are being driven to the road of death,'' they said in a statement.
There was no immediate reaction from Hong In-ki, head of the Korea Stock Exchange, who was out of his office during the three-hour protest.
The union leaders said they and supporters from other labor groups would stage a larger protest rally at the stock exchange Wednesday.
They demanded that President Kim Young-sam, attending an Asia-Pacific Economic Cooperation forum meeting in Vancouver, cut short his stay and return home.
Stock prices, which had been slumping for weeks, began a sharp drop last Saturday, a day after South Korea asked the International Monetary Fund to bail out its troubled economy.
Analysts said investors fear that more shaky companies will be forced into bankruptcy by the strict conditions usually attached to IMF loans.
On Tuesday, the benchmark Korea Composite Stock Price Index dropped 11.05 points, or 2.45 percent, closing at 439.59, its lowest level since July 1987. On Monday, the index had fallen 7.2 percent to 450.64.
In the financial district, investors stared dejectedly at trading screens lit up with yellowish green lines indicating that the market was full of declining issues, with few advances.
``In the past several days, I hated to look at the screens,'' Kim Jin-man, 72, an investor, said. ``I have seven to eight years of experience in stock investing. I lost most this time.''
South Korea is the latest Asian country to go to the IMF for help since the July plunge of the Thai currency. Thailand, Indonesia and the Philippines also are receiving IMF help.
IMF and South Korean officials are negotiating the terms of the loan package. The IMF is likely to order deep spending cuts, higher taxes, the elimination of shaky banks and businesses, and the forfeiture of some national decision-making power.
In New York, Lee Kyung-shik, governor of the central Bank of Korea, said the $20 billion bailout being sought by his government may be too small. He indicated that the amount would rise to $50 billion.
``The investor sentiment is still very unstable,'' Baek Jung-hyun, an analyst at Samsung Securities Co., said. ``If closing the stock market could be an option, they should have done it a long time ago. It's too late to consider it now.''
South Korea has already announced an overhaul of its inefficient finance sector, mainly aimed at forcing mergers and acquisitions among the nation's smaller merchant banks.