North Korea fired two short-range missiles into the ocean Monday in an apparent response to the kickoff of the longest U.S.-South Korea annual military exercise.
"North Korea launched two missiles that are being assumed short-range ballistic missiles, having a range of more than 490 kilometers [304 miles], in the direction to the East Sea from Nampo between 6:32 a.m. and 6:41 a.m. today," according to a statement from the South Korean Joint Chiefs of Staff office.
Nampo is a city on North Korea's west coast, and the East Sea is also known as the Sea of Japan.
South Korean defense officials told Stars and Stripes they believe the launches were a response to the start of the Key Resolve and Foal Eagle exercises, which include several thousand U.S. and South Korean troops.
"Our military is watching for the possibility of additional North Korean launches and various provocations, while maintaining a readiness posture," a Joint Chiefs of Staff spokesman said on condition of anonymity, which is customary.
Last year, North Korea launched missiles off its east coast in advance of the exercises, and has taken similar measures in the past. Each time, North Korean media has denounced the Key Resolve and Foal Eagle exercises as acts of aggression.
A statement from North Korea's army, sent prior to Monday's missile launches, threatened South Korea with a "merciless baptism by fire," Ministry of Defense spokesman Kim Min-seok told reporters Monday.
Such hyperbole is relatively common from Pyongyang. In 2013, North Korea threatened to turn the South's presidential palace into a "sea of fire" on the three-year anniversary of its shelling of Yeonpyeong Island, which killed four South Koreans.
"North Korea's threatening words and actions are enormously serious challenges to security on the Korean Peninsula, and its provocative action to launch ballistic missiles is a clear violation against U.N. security resolutions," Kim said.
Key Resolve, a command post exercise running through March 13, will be observed by Australia, Canada, Denmark, France and the United Kingdom. The Neutral National Supervisory Commission will monitor the exercise, in accordance with the 1953 United Nations armistice agreement with North Korea.
Foal Eagle is a series of land, air, naval and special operations exercises running through April 24.