China and Russia have joined a unanimous UN vote to impose new sanctions on North Korea after its sixth and largest nuclear test.

The council voted 15-0 to back the US-drafted sanctions resolution banning exports of coal, lead and seafood.

Pyongyang has claimed to have developed a hydrogen bomb and has continuously threatened to strike the US.

North Korea is already under UN sanctions to force the leadership to curtail its weapons programmes.

The new sanctions were agreed on Monday after the US removed some of the tougher proposals it had announced last week, including a complete oil embargo and measures to freeze the assets of North Korean leader Kim Jong-un.

US President Donald Trump had previously warned that the US could cut off trade with countries that did business with North Korea.

In August, a new round of US sanctions banned exports including coal, costing North Korea an estimated $1bn (£767m) – about a third of its entire export economy.

Both China and Russia had been pushing for an alternative solution.