"The two Koreas exchanged artillery fire across the western maritime border on Monday after the North staged a live-fire drill that sent artillery shells into southern waters and prompted the evacuation of South Korean islanders," South Korea's Yonhap News writes.
"The exchange, triggered by a three-hour North Korean live-fire exercise that dropped shells into South Korean waters, was limited to untargeted shelling into the sea, military officials said.
"South Korea's Defense Ministry said the North fired some 500 shells during the drill, around 100 of which landed on the south side of the sea boundary.
"Ministry spokesman Kim Min-seok said the South had responded to Pyongyang's 'premeditated provocation' by firing 300 shells from K-9 self-propelled howitzer batteries located on its front-line islands."
According to the Los Angeles Times, North Korea's behavior could be an attempt by its leaders to again register their objection to U.S.-South Korea military exercises that are now underway.
Reuters calls the incident "more saber rattling from Pyongyang rather than the start of a military standoff."
The sense that the North was blustering was underscored by the fact that it alerted the South to the live-fire exercise in advance — "in a faxed message from its military to the South's navy," the BBC says.
The dangers of what can happen when the North decides to show its displeasure with joint U.S.-South Korean exercises and with disputed territories were highlighted in November 2010, however. Two South Korean civilians and two South Korean military personnel were killed by shells the North fired that hit an island off the peninsula's western coast.
It was "the worst act of aggression against South Korea" since the 1950s, according to Dongseo University international studies professor Brian Myers.