North Korea is threatening to turn South Korea into "debris" unless it stops activists sending anti-North propaganda leaflets across the border.

Activists from the South have been sending the leaflets into North Korea attached to balloons.

But recent leaflets speculating on the health of the North's leader, Kim Jong Il, have prompted an angry response from Pyongyang.

The North's military used cross-border military talks to warn the South it would strike pre-emptively and reduce South Korea to "debris" in a "just war".

Separately, Japan's Prime Minister says his government has information that North Korean leader Kim Jong Il is in hospital.

Taro Aso says the 66-year-old appears still capable of making decisions, despite reports earlier this year he may have suffered a stroke.