Reports said a surge by up to 50 protesters -- many described as militant South Korean farmers opposed to the lowering of trade barriers -- was repelled by police who used pepper spray and batons.
There were no immediate reports of serious injuries.
At least nine people were reported injured as the six days of trade liberalization talks got under way yesterday.
In the negotiations, the world's poorest countries are seeking a reduction in the tariffs put on mainly agricultural goods they sell to richer countries. Richer countries say they hope that a fairer deal, combined with development aid, will encourage the poorer countries to support lowering trade barriers on manufactured goods and services from wealthier countries.