North Korea stages live-fire military drill prompts South to return fire

North Korea has fired artillery shells into South Korean waters, apparently in reaction to military exercises being conducted between the U.S. and South Korea.Seoul responded immediately on Monday by shelling North Korean waters. Officials say no shells hit any land areas on either side and no one was injured. South Korean officials said some residents of border islands were evacuated to shelters as a precaution.

The North in recent weeks has increased threatening rhetoric and conducted a series of rocket and ballistic missile launches into waters off the west coast of the Korean peninsula.Pyongyang threatened on Sunday to conduct what it called "a new form of nuclear test" after the U.N. Security Council condemned the North's recent ballistic missile launches.

A statement Sunday from the North's Foreign Ministry said it was intolerable that the Security Council would "turn a blind eye" to U.S. nuclear war exercises while denouncing the North Korean army's self-defensive rocket launch exercises.After North Korea fired two medium-range ballistic missiles into the sea off the east coast of the Korean peninsula Wednesday, the Security Council condemned the launches the next day, saying they violated U.N. resolutions.

Pyongyang routinely calls military drills between South Korea and the U.S. a rehearsal for invasion.