North Korea ratifies major defence treaty with Russia

Vladimir Putin and Kim Jong Un pose for a photo during a signing ceremony of the new partnership in Pyongyang, North Korea, in June - (AP)

North Korea has ratified a major defence treaty with Russia that promises mutual military aid between the two nations, the North's state media has reported.

It comes as the US, South Korea and Ukraine say North Korea has sent thousands of troops to Russia to support its war against Ukraine.