North Korea has warned that the world is on the brink of “thermo-nuclear war” as fears rise that Pyongyang is planning a test of military hardware that could provoke a response from President Donald Trump.

Tensions over the North’s nuclear ambitions escalated further on Friday after reports in the US that Washington was ready to launch a pre-emptive strike, while China called for all sides to pull back from an “irreversible and unmanageable stage”.

Evidence of increased activity in recent weeks at the North's nuclear test sites has sparked fears that the country may be about to conduct its sixth nuclear test since 2006 at the weekend.