Thousands of anti-globalization protesters rallied in Seoul on Sunday against a summit of the world's leading economies taking place in the South Korean capital this week, DPA reported.
Organizers said said 40,000 people took part in the protest against the Group of 20 (G20) meeting, but police put the figure at half that.
Television footage showed scuffles between riot police and demonstrators in Town Hall Square. Police used pepper spray to disperse a group that tried to march through the town centre.
The protesters chanted slogans against the November 11-12 gathering of world leaders and carried banners reading "We are the G20."
Other slogans were directed against a free-trade agreement singed between host nation South Korea and the United States.
Unions and non-governmental organizations who organized the protest accuse the G20 nations of failing to take measures to create jobs and making poorer countries pay for the financial crisis that brought the global economy to its knees two years ago.
The G20 will be taking place amid heavy security, with some 50,000 police officers mobilized to protect delegates against terrorist threats and clamp down on angry protesters.