NORTH AND SOUTH Korea say they have exchanged warning shots along their disputed western sea boundary.

South Korea’s military says its Navy fired warning shots to repel a North Korean merchant ship that it says violated the sea boundary early this morning.

North Korea’s military said it responded by firing 10 rounds of artillery shells as a warning to South Korea.

The incident comes amid heightened tensions over North Korea’s recent barrage of missile tests.

The poorly marked sea boundary off the Korean Peninsula’s west coast is a source of long-running animosity between the two countries. It is a scene of several bloody inter-Korean naval skirmishes and violence in recent years, including the two attacks in 2010 that killed 50 South Koreans.

In recent weeks, North Korea has carried out a string of weapons tests in response to what it calls provocative military drills between South Korea and the United States.

Since 25 September, North Korea has fired 15 missiles and hundreds of artillery shells toward the sea.

Seoul and Washington routinely conduct military drills to maintain their readiness against potential North Korean aggressions. The allies say their drills are defensive in nature, but North Korea views them as an invasion rehearsal.

South Korean military is under annual field exercises set to end this Friday. This year’s drills involve an unspecified number of US troops.

Some experts say North Korea’s recent weapons tests are also designed to bolster its arsenals to boost its leverage in future negotiations with its rivals.