More Drills Between U.S. And South Korea

The U.S. and South Korea are conducting more military exercises, despite the growing tension with North Korea.

The North has warned the drills are a "grave military provocation" that will spark retaliation.

Both the U.S. and the South Korean governments said the computer simulated war games are annual, routine and purely defensive.

Almost 86,000 troops are involved, 30,000 of which are American.