North Korea released a report on Thursday defending last month's deadly attack on a South Korean island, accusing Seoul and Washington of "persistently escalating tension" in disputed seas off its west coast.
The North fired a barrage of artillery shells at Yeonpyeong, one of five South Korean islands straddling the contested Northern Limit Line (NLL) sea border, killing four people, including two civilians.
The shelling, the first of its kind against civilians on South Korean soil since the end of the 1950-53 war, coupled with the North's revelations of nuclear advances giving it a second path to make an atomic bomb, have spiked tensions on the peninsula.
Pyongyang said it had fired artillery at the island after South Korea had fired into its waters. Seoul said it had only been conducting regular military drills in the area at the time.
South Korea "fired as many as thousands of shells into the territorial waters of the DPRK side," the state news agency quoted the Secretariat of the Committee for the Peaceful Reunification of Korea report as saying.
"This reckless act was obviously a deliberate provocation to prompt the DPRK to take a military counter-action," it said.
Pyongyang does not recognize the NLL, arguing that the demarcation was established without its consent after the 1950-1953 Korean war.
There have been several deadly battles in the area over the past decade, and in March a South Korea warship was sunk killing 46 sailors.
"The above-said island is located deep inside the territorial waters of the DPRK side from the maritime demarcation line," the report said.
"If any live shell firing is conducted from there, shells are bound to drop inside the territorial waters of the DPRK side no matter in which direction they are fired because of these geographical features of the island."
Both Koreas frequently conduct drills in the area.
The statement also said the South had "persistently mocked at the DPRK's sincere efforts to improve the inter-Korean relations and turned away their faces from them."
The North has said it wants to resume six party nuclear talks, but Washington and Seoul have said they will only consider a return to the negotiating table when Pyongyang shows it is sincere about denuclearization.