|Last November's attack on Yeonpyeong island damaged houses and left four South Koreans dead [EPA]
North Korea has fired artillery in the direction of a South Korean island in an apparent training exercise, according to South Korean media and a government official.
A South Korean defence ministry official said the shells landed in the waters off Yeonpyeong island on Tuesday but it was not clear whether it was inside the South's territorial waters.
Yonhap news agency said South Korea fired back with its artillery. It said the shelling started at about 2pm local time (0500 GMT).
"Three shots were heard. One shell landed near the Northern Limit Line," Yonhap quoted a military official as saying.
The incident took place near the disputed Northen Limit Line (NLL), the scene of several skirmishes over the past decade.
Fishing boats in the vicinity called to port and Yeonpyeong residents have been evacuated into emergency shelters, media reports said.
Last November four South Koreans - two civilians and marines - were killed on the island when the North shelled part of Yeonpyeong.
And in March 2010, a South Koren navy ship, Cheonan, was ripped into two by an explosion, killing 46 sailors. Pyongyang denied any involvement but international investigators suggested the North bore responsibility for the incident.
The line separating North and South Korea, drawn at the close of the 1950-53 war between the two nations, remains a fierce point of dispute.
North Korea argues that the line should run farther south, but Seoul fears it would endanger fishing around five South Korean islands and hamper access to its port at Incheon.
The November attack marked a new level of hostility along the contested line.
Tensions had eased since the start of the year after the North's renewed calls for dialogue, including the resumption of six-party talks aimed at ending Pyongyang's nuclear arms programme.
The two Koreas, Russia, the US, Japan and China are involved in the on-off disarmament talks.