North Korea has threatened to void the armistice that ended the Korean War. (Creative Commons)

After the start of the drills, South Korean officials confirmed that their neighbors to the north did not answer two calls on a hotline between the two sides, apparently following through on a vow to cut off communication with the South because of the drills. Pyongyang wants a formal peace treaty, security guarantees and the removal of 28,000 U.S. troops based in South Korea.

Although North Korea isn't believed to be capable of building a warhead small enough to mount on a long-range missile, South Korean and U.S. officials are keeping an eye on the recent rhetoric from the North, which has become more hostile than usual.

North Korea possesses a variety of missiles capable of striking South Korea. The North shelled a South Korean island and torpedoed a warship belonging to the South in 2010, killing a total of 50 South Koreans. The U.S. has troops stationed in South Korea to prevent North Korean aggression due to years of tension stemming from the Korean War.

Read the full story at the Associated Press. Find more Neon Tommy coverage of North Korea here.

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