South Korea has found the bodies of two civilians who were killed Tuesday in a North Korean artillery attack on the island of Yeonpyeong near the disputed maritime border. The attack also killed two Korean marines and injured over a dozen people. U.N. Secretary-General Ban Ki-moon called Tuesday’s fighting one of the “gravest incidents” since the end of the Korean War. Meanwhile, the Guardian newspaper reports South Korea’s defense minister has raised the possibility that U.S. nuclear weapons could be deployed in his country for the first time in nearly 20 years.