Communist North Korea Saturday demanded the United States and South Korea halt joint military exercises and accused the U.S. Air Force of staging simulated nuclear attacks with B-52 bombers on the Korean peninsula.

U.S. officials denied North Korean charges as propaganda. U.S. forces in South Korea are believed to have nuclear weapons, but Washington has declined to confirm or deny such reports.Students in the South Korean capital Seoul and the southern city of Kwangju battled police with firebombs and rocks Saturday to demand an end to the "Team Spirit" exercises and an immediate withdrawal of U.S. troops based in South Korea.