US and South Korea Begin Joint Navel Exercise

North Korea has threatened a "physical reponse" to upcoming joint military exercises between the United States and South Korea, saying they pose a grave danger to security in the region.

The warning came from Ri Tong-il, a member of North Korea's delegation to the Asean Regional Forum, Asia's largest security summit, in Hanoi on Thursday.

The exercises near the Korean Peninsula come four months after the sinking of the South Korean warship Cheonan, an incident that killed 46 sailors and has been blamed by Seoul and Washington on the North. Pyongyang insists on its innocence and threatened to respond to this week's drills with "a powerful nuclear deterrence" and "sacred war."