Cracks discovered in a North Korean dam, immediately north of the Korean border, have raised concerns in South Korea.

The 16-year-old Kumgangsan dam lies on a northern tributary of the Han river which flows across South Korea and through the capital Seoul.

The South Korean government has said it would take the precaution of emptying dams on its side of the border, to store any massive flows of water due to a failure of the dam.