North Korea fired two short-range missiles off its east coast on Monday, a South Korean military official said, a move seen as a protest against annual military exercises between South Korea and the United States that were due to start hours later.
The missiles hit the sea early on Monday morning after traveling for about 490 km (305 miles), the official said.
The firing came on the day when the U.S.-South Korean military exercises were scheduled to begin. The secretive North denounces the drills as a preparation for war.
Pyongyang has escalated its rhetoric against the drills, with a spokesman for its army general staff saying Washington and Seoul "should be dealt with only by merciless strikes".
North Korea frequently tests short-range missiles off its coast as part of military drills.
The United Nations has imposed sanctions banning North Korea from launching longer-range ballistic missiles but not short-range missiles.