South Korean defense officials say their navy has fired warning shots at a North Korean patrol boat as it briefly crossed a disputed maritime border to the west of the peninsula.
The incursion Friday came on the same day the Asian Games officially opened in the South, with North Korean athletes participating.
South Korea's joint chiefs of staff said the boat crossed the Northern Limit Line in the Yellow Sea just after noon, but it returned to its territory six minutes later as the South Korean navy fired the warning shots.