After heavy rain on the Korean peninsula, North Korea has told the South it may soon have to release large quantities of water from a dam just north of the border.
The notification, made through a military communications line, contrasts with an unannounced discharge of 40 tonnes of water by North Korea last autumn.
That incident caused a river surge in the South and killed six people.
The warning appears to be the first conciliatory gesture from the North since the sinking of a South Korean warship in March.