North Korea has told Britain it cannot guarantee the safety of diplomats after 10 April in the event of a conflict, the British foreign ministry said.
The Foreign Office said its embassy in Pyongyang received a communication from the North Korean government this morning.
It said it would "be unable to guarantee the safety of embassies and international organisations in the country" in the event of conflict.
The British government is "considering next steps" after the North Korean administration asked diplomatic missions if they were planning to evacuate.
It described the request as part of North Korean's "rhetoric" against the US.
Earlier, China's official Xinhua news agency cited diplomatic sources as saying that North Korea has also told foreign embassies to consider the possibility of evacuating if tensions flare.
The agency did not elaborate in its brief report.
Russian Foreign Minister Sergei Lavrov said Moscow was in close contact with the US, China, South Korea and Japan over the request.
Meanwhile, North Korea has placed two of its intermediate range missiles on mobile launchers and hidden them on the east coast of the country, South Korea's Yonhap news agency has reported.
The report could not be confirmed, but may be intended to demonstrate a threat by the North to either Japan or to US bases on Guam.
The North has threatened to attack bases on Guam if the US launches a strike on it.
South Korea's Defence Ministry has declined to comment on the report.
There were also unconfirmed media reports that the North had moved missiles to the east coast yesterday, although it was not clear what kind of missiles had been deployed.
Speculation has centred on two kinds of missiles, neither of which is known to have been tested.
One was the Musudan missile, which South Korea's Defence Ministry estimates has a range of up to 3,000km.
The other missile is called the KN-08, which is believed to be an inter-continental ballistic missile, which is again untested.
South Korea's defence minister has said he does not believe the missile that was moved was the KN-08.
North Korea has slowly and steadily improved its missile capabilities in recent years.
US officials say its missiles may be capable of hitting outlying US territories and states, including Guam, Alaska and Hawaii.
Some experts say even this view is alarmist.
There is no evidence the officials say that North Korea has tested the complex art of miniaturising a nuclear weapon to be placed on a long-range missile.
Miniaturising is a capability the US, Russia, China and others achieved decades ago.
North Korea has been engaged in a month-long war of words with the US and South Korea in the wake of UN sanctions imposed for its February nuclear test.
It has threatened to stage a nuclear strike on the US, to attack bases on Guam and said a state of war exists on the Korean peninsula.