S Korea fires shots at North's ships

South Korea says its navy has fired warning shots to drive away North Korean patrol ships that had crossed the western maritime border between the two countries.

The two North Korean vessels violated a disputed inter-Korean border in the Yellow Sea, known as the 'Northern Limit Line', on Saturday night, South Korea's military said.

"Two patrol boats crossed on two separate occasions and warning shots were fired," BBC quoted a South Korean official as saying on Sunday.

The first North Korean vessel retired after a South Korean ship broadcast a warning and the second vessel retreated after a couple of warning shots were fired, said the official, on condition of anonymity.

The incident is the most serious skirmish between the two nations since a South Korean warship was mysteriously sunk in March.

Seoul suspects that a North Korean torpedo hit the military vessel but Pyongyang has denied being responsible for the sinking.

The Northern Limit Line was set in the 1950s in the wake of the Korean War. North Korea does not recognize the United Nations-specified border, but South Korea keeps it as a de facto border.