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.

The United Nations' highest court on Wednesday underlined "the urgent and existential threat posed by climate change" as it started to read out an opinion on the legal obligations of states to take action.

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