North and South Korea have exchanged fire into the sea across the disputed western sea border, South Korea says.North Korea announced early on Monday that it would hold live-fire drills in seven parts of the border area.
South Korea says it returned fire after North Korean shells landed in its territorial waters.
The area has been a flashpoint between the two Koreas. The UN drew the western border after the Korean War, but North Korea has never recognised it.
In late 2010, four South Koreans were killed on a border island by North Korean artillery fire.
‘Responded with fire’
The live-fire exercises were announced by North Korea in a faxed message from its military to the South’s navy.
The exercises would take place in seven border areas, the message said.
South Korean had warned of immediate retaliation if any ordinance crossed the border.
“Some of the shells fired by North Korea dropped in our area and our side responded with fire,” a military spokesman told AFP news agency.
“For the moment, both sides are firing into the sea.”
Residents of a border island were evacuated into shelters, reports said.
In November 2010, North Korea fired shells at the border island of Yeonpyeong, killing two marines and two civilians.
It said it was responding to South Korean military exercises in the area.
Earlier that year, a South Korean warship sank near the disputed border with the loss of 46 lives.
Seoul says Pyongyang torpedoed the vessel but North Korea denies any role in the incident.
The latest incident comes days after North Korea test-fired two medium-range Nodong missiles over the sea, its first such launch since 2009.
Late last week, the UN Security Council condemned the launch and said it was considering an “appropriate response”.
That launch followed a series of short-range missile tests, seen as a response to the current US-South Korea annual military exercises.
Over the weekend, North Korea also threatened to conduct a “new form” of nuclear test.
It has conducted three nuclear tests to date, the most recent in February 2013.
