One of the world’s most vulnerable countries to the fallout from climate change has won a landmark legal battle, giving countries new ammunition to pursue some of the planet’s biggest emitters.

The International Court of Justice called global warming an “urgent and existential threat” at a closely watched case in The Hague.

The UN's top court on Wednesday ruled climate change an "existential problem of planetary proportions" and said countries had a legal duty to act or face consequences.