SEOUL, South Korea -- South Korea says there could be a considerable number of North Korean casualties, from its response to North Korea's shelling of an island near their disputed border today.
The shelling killed at least two South Korean marines, and set dozens of buildings on fire on an island where there is a small civilian population living alongside military installations.
South Korea returned fire and sent up fighter jets in response.
The shelling followed a North Korean demand that South Korea stop its military exercises on the island. The South refused.
North Korea's supreme military command is warning of more strikes if the South makes even the smallest incursion over their maritime border.
The clash marked a sharp escalation of the skirmishes that flare up along the disputed border from time to time. It comes amid high tensions over North Korea's claim that it has a new uranium enrichment facility.