About 100,000 South Koreans staged an anti-Communist rally on Monday, clashing with police and burning North Korean flags to press their calls for an end to the Pyongyang regime and its suspected nuclear arms programmes.
The rally at Seoul's City Hall plaza in the heart of the capital drew mostly elderly people, including Korean War veterans and Christians - conservative groups critical of the conciliatory North Korea policies of President Roh Moo-hyun.
"Kim Jong-il has nuclear weapons and is threatening the international community. The free world must co-operate to get rid of this terror and anti-state regime," said protest leader Park Chan-sung. Kim is the leader of reclusive North Korea.
The protest comes amid uncertainty over the fate of talks to end a stand-off over North Korea's nuclear ambitions and efforts by the South's ruling centre-left Uri Party to scrap decades-old legislation banning contact with the communist North.
Toward the end of the four-hour rally, some protesters armed with flagpoles and wooden clubs clashed with riot police and climbed on police buses in failed efforts to reach the presidential Blue House.
Several war veterans brought in vehicles to battle police water cannon before retreating after at least 10 protesters were injured.
Following Christian prayers, protesters burned North Korean flags and carried a mock plastic missile to denounce the North's nuclear programme. Marchers carried placards saying "Down with Kim Jong-il!" and "Support North Korean Human Rights".
The crowd, which police said reached 100,000 people, also took aim at Roh's government and his Uri Party, accusing them of being soft on North Korea.
"Preserve the National Security Law to the death," protesters chanted in an attack on the Uri Party's attempts to scrap the anti-Communist law. Roh's backers say the law is a relic of the country's 1970s and 1980s military dictatorships.
The National Security Law uses sweeping provisions to jail those who work for enemies of the state, notably North Korea, and their sympathisers. It technically bans the kind of contacts with the North that have become commonplace in recent years.
Human rights critics say former leaders used the law to quell dissent and that it is redundant. Uri Party members, many former dissidents, suffered under the law in previous decades. The debate in parliament over scrapping or revising the law has taken on a bitter ideological tone because North Korea has consistently demanded the repeal of the legislation.
Conservative lawmakers argue that the security law is still needed because North Korea has never renounced its goal of overthrowing the South by force, as Pyongyang tried to do when it invaded in 1950, sparking the three-year Korean War.