SEOUL: Seoul Friday accused North Korea of a "blatant lie" in claiming it had not fired shells near a South Korean warship and said Pyongyang had threatened to bombard its military vessels.
The North's military earlier Friday had rejected as "sheer fabrication" Seoul's assertion that it fired two shells in the vicinity of a South Korean navy vessel on patrol near the tense sea border Thursday.
Seoul's defence ministry said the shells fell about 150 metres (yards) off the South Korean Navy corvette near the disputed sea border in the Yellow Sea.
The ship was not damaged and responded by firing five rounds into waters near a North Korean military vessel.
"The verified fact is that the puppet navy vessel, which intruded deeply into our waters under the pretence of controlling Chinese fishing boats, fired recklessly and lied that we had fired first. This is a sheer fabrication", North Korea's military Western Front Command said in a statement.
"All the troops under the Western Front Command are well prepared to crush ruthlessly the aggravating provocative acts by the puppet military gangsters in the name of all the people".
It then vowed to turn the tense sea border area into "tombs" for the South's military.
But South Korean defence ministry spokesman Kim Min-Seok stood by Seoul's charges and dismissed the North's claim as a "blatant lie".
"North Korea's such far-fetched claims are nothing but a blatant lie ... and are subject to ridicule by the international community," he told journalists.
A South Korean military Joint Chiefs of Staff spokesman said Friday the North continuously sent messages through an international radio channel, threatening attacks on the South's military vessels operating near the sea border.
"Recently, it has been threatening to bombard our ships unless they pull back" from the sea border, he said.
South Korean President Park Geun-Hye on Friday expressed "very strong regret" that North Korea committed this "provocation" at a time when South Koreans are in grief over last month's ferry sinking, her spokesman Min Kyung-Wook said.
The build-up to the incident started Tuesday when a South Korean naval ship fired warning shots to turn back three North Korean patrol boats that crossed the disputed sea boundary.
North Korea then threatened Wednesday to launch an attack on South Korean warships without warning at the slightest hint of any provocative act, claiming the North Korean patrol boats were controlling illegal Chinese fishing boats north of the unmarked sea border.
The North does not recognise the Northern Limit Line as a sea border, unilaterally drawn in the Yellow Sea by the US-led United Nations at the end of the Korean War.
It was the scene of brief but bloody naval clashes in 1999, 2002 and 2009.
In March the North fired hundreds of shells in a live exercise near the sea boundary. About 100 shells dropped into South Korean territorial waters, and the South responded with volleys of shells into North Korean waters.
Cross-border tensions have been high for months and both sides have upped the ante in their verbal exchanges over crashed surveillance drones recently recovered on the South Korean side of the border.
Seoul said a joint investigation with US analysts had provided "smoking gun" evidence that the drones came from the North. Pyongyang flatly denied any involvement.