South Korea has accused the North of intentionally causing a flash flood south of their heavily fortified border that killed six South Koreans, Press TV reported.
On Sunday, a sudden discharge of water from a North Korean dam into a cross-border river caused a surge that carried away campers on the South Korean soil.
"I think the North did it intentionally," Unification Minister Hyun In-Taek told parliament on Wednesday to become the first Seoul official to publicly claim that the release of the water was deliberate.
Pyongyang on Monday said the release was an emergency that could not be helped due to the surge in the Hwanggang Dam's water level, and promised prior warning in case of future discharges.
But officials in Seoul argue that there had been no heavy rain in the North in recent days to explain discharging an estimated 40 million cubic meters (52 million cubic yards) of water, demanding an apology and full explanation from its communist neighbor over the incident.
While South Korea remains critical of the North for failing to express regret for the incident, the tragedy is feared to jinx a recent improvement in cross-border relations.
In August, the North freed five South Korean detainees, eased border restrictions and sent envoys for talks with the South's President Lee Myung-Bak.
Unannounced discharges from North Korean dams have repeatedly hit fish farms and riverside areas south of the border but the Sunday incident was the first to claim lives.
Among the victims was an eight-year-old boy, whose body was recovered from the Imjin river on Wednesday along with two others, in addition to three found earlier.
South Korean Defense Ministry says it will deploy aircraft and a pilotless drone to step up surveillance over North Korean dams upstream to prevent any 'water attacks'.