North Korea says the urgent discharge of dam water on Sunday that left six South Koreans dead or missing was due to a rise in upper stream water levels.

In a Monday reply to Seoul’s request for explanation for the incident, Pyongyang said increased water levels at a dam in the upper river area forced the North to discharge water from Saturday night through Sunday morning.

The North said it will notify Seoul in the future before any water is discharged from its dams.

The Unification Ministry in Seoul says North Korea’s explanation is not sufficient and lacks any remorse regarding South Korean casualties.

The ministry says it will seek inter-Korean talks to institute measures on flood prevention and joint use of the rivers that flow southward across the inter-Korean border.