Subscribe to the BlogSouth Korea has referred North Korea to the United Nations over the sinking of its warship in March.
An international investigation found that North Korea was responsible, an accusation the North denies.
South Korea has not spelled out what action it wants the UN to take, although it has not asked for sanctions against the North.
Tensions between the two Koreas have increased since the sinking in which 46 sailors were killed.
In a speech to an Asian security conference in Singapore, South Korean President Lee Myung-Bak said: "North Korea must admit its wrongdoing."