Seoul – Pyongyang on Friday condemned the South Korean navy's seizure of a North Korean fishing boat near the disputed sea boundary as a "grave provocation" and threatened to retaliate.
The warning was issued by a spokesperson for the North Korean army's general staff after South Korea handed back the boat which was captured with three sailors aboard near the disputed Yellow Sea border late Thursday.
"KPA [Korean People's Army] will never pardon gangsterism of South Korean military warmongers," the spokesperson said in a statement released through the country's official Korean Central News Agency.
South Korea said the vessel had intruded into its territory and refused to retreat despite warning shots.
An overnight investigation found the vessel could not sail north because of a sudden engine failure, the South's Joint Chiefs of Staff said.
The vessel was handed over to a North Korean naval ship early on Friday after its crew told investigators that they had no intention to defect and requested to return to their homeland, it said.
The South's navy has told its North Korean counterpart that the seizure was aimed at ensuring the safety of the crew.
The North Korean spokesperson, however, insisted that South Korean naval ships had sailed north across the sea boundary, fired about 50 shots "recklessly" to seize the vessel, and beat its sailors with iron sticks.
They were taken to a front-line South Korean island for investigation after being "shackled and blindfolded", he said.
"We will never overlook the inhumane and monstrous atrocities committed by South Korean military warmongers by forcibly seizing the fishing boat and committing gangster-like crimes against its crew," the spokesperson warned.
The maritime border, which Pyongyang does not officially recognise, was the scene of brief but bloody naval clashes in 1999, 2002 and 2009.
North Korean incursions over the maritime border are not unusual.
A North Korean patrol boat violated the sea boundary on 25 February at the start of South Korea-US military drills, and retreated after warnings from the South Korean navy.
Thursday's incursion came after nearly 15 000 South Korean and US troops kicked off a 12-day amphibious landing drill, the largest for two decades, off the South's southeast coast.
North Korea views such exercises as provocative rehearsals for invasion and there is a risk they could further fuel already simmering military tensions.
Pyongyang has carried out a series of rocket and short-range missile launches in recent weeks, sparking condemnation from Seoul and Washington.
On Wednesday, it test-fired two mid-range ballistic missiles capable of striking Japan.