Protesters in Seoul chant anti-nuclear slogans.
The demonstration comes a day before a Nuclear Security Summit of more than 50 world leaders.
Protesters are calling for an end to both nuclear power and nuclear weapons.
(SOUNDBITE) (Korean) PROTEST LEADER LEE HEON-SEOK
"We are here to protest against the Nuclear Security Summit. We want nuclear weapons and nuclear plants to be scrapped. The nuclear summit does not discuss these issues."
Across the city, nuclear supporters hold their own demonstration.
(SOUNDBITE) (Korean) CO-CHAIRMAN OF FUTURE ENERGY COALITION, KIM DONG-WON
"It is necessary to discuss the future of energy, for the future of mankind. We'd like the world leaders to make every effort for a successful nuclear security summit."
Plans by North Korea to launch a long-range missile next month are expected to take centre stage at the two-day summit.
Jessica Gray, Reuters
