British officials in North Korea have been warned authorities there would be unable to guarantee their safety in the event of conflict, as Pyongyang upped the pressure in a war of words that has set the Korean peninsula on edge.

It is understood the Foreign Office has no intention of evacuating the mission in the capital Pyongyang despite the North Korean regime saying it could not protect embassies and international missions if war broke out after April 10.

Initial reports had suggested embassies consider closing because of the risk of conflict.

A British diplomatic official said European Union embassies in Pyongyang had been summoned to deliver their evacuation plans.

The Foreign Office is "considering next steps", including the possibility of amending travel advice, but it warned North Korea that it had obligations under the international Vienna convention to protect diplomatic missions and claimed the move was an example of the "continuing rhetoric" against the United States.

Prime Minister David Cameron has warned that Kim Jong-un's regime possessed weapons that could threaten the UK.

"North Korea does now have missile technology that is able to reach, as they put it, the whole of the United States," he said.

"If they are able to reach the whole of the US they can reach Europe too, they can reach us too. That is a real concern."

The latest crisis in relations on the Korean peninsula follows anger in Pyongyang about sanctions against its nuclear programme and joint military drills involving US and South Korean forces.

The North's military warned on Thursday that it had been authorised to attack the US, and South Korea's defence minister claimed its neighbour had moved a missile with "considerable range" to the east coast, potentially able to hit targets in the South or Japan.

The report could not be confirmed, but any such movement may be intended to demonstrate that the North is prepared to demonstrate its ability to mount an attack.

Speculation centred on two kinds of missiles, neither of which is known to have been tested.

One was the so-called Musudan missile, which South Korea's Defence Ministry estimates has a range of up to 1865 miles.

The other, called the KN-08, is believed to be an inter-continental ballistic missile.

South Korea has reportedly deployed two warships with missile-defence systems in response.

While few observers believe that North Korea will launch a military attack, alarm has grown over the intensification of the threats from its 30-year-old leader.

Mr Kim is the third member of his family to rule in Pyongyang and took over in December 2011 after the death of his father Kim Jong-il, who staged confrontations with South Korea and the United States throughout his 17-year rule.

"We don't understand this new guy at all," said Victor Cha, a former director for Asian affairs at the White House National Security Council.

"And if the North Koreans move to provoke the South, the South is going to retaliate in a way we haven't seen before."