Authorities in the North Korean capital have warned foreign embassies that it cannot protect them in the event of nuclear war.

Pyongyang says if the conflict escalates the government will not be able to guarantee the safety of embassies and international organisations beyond April 10th.

In response the UK Foreign Office says it has "no intention" of evacuating its embassy.

The moves come as North Korea announced it has now moved two intermediate range missiles to its east coast and loaded them on mobile launchers.

North Korea 'real & clear danger', says US

The United States meanwhile is reinforcing its Pacific missile defences and preparing to send ground-based interceptors to Guam.

It comes after North Korea said Thursday it had authorised plans for nuclear strikes on US targets.

The US Secretary of Defence Chuck Hagel said the threats combined with the military capabilities of Pyongyang represented a "real and clear danger" to the United States and to its allies.

"They have nuclear capacity now, they have missile delivery capacity now" he said Wednesday. "We take those threats seriously, we have to take those threats seriously" he added.

The United Nations Secretary-General Ban Ki-moon has said the crisis has gone too far already.