North Korea has told foreign embassies in Pyongyang to consider evacuating staff by next week because it will be unable to guarantee their safety in the event of any conflict.

European countries with embassies in Pyongyang including Britain and Russia have confirmed they have received the warning advisory.

A spokesman from Britain's foreign office said Pyongyang had warned in the notice that "from April 10 [it] would be unable to guarantee the safety of embassies and international organisations in the country in the event of conflict".

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 3 minutes 10 seconds 3 m 10 s Embassy staff warned to leave North Korea Download 1.5 MB

The statement said there were no immediate plans to withdraw diplomats, adding that the warning may simply be further sabre rattling from Pyongyang.

"Our understanding is that the North Koreans were asking whether embassies are intending to leave, rather than advising them to leave," a spokeswoman said.

Russia's foreign minister Sergei Lavrov said Moscow, which has relatively close ties with Pyongyang, was consulting with China, the United States and other members of the stalled six-party talks on North Korea.

Mr Lavrov said he was concerned by the diplomatic escalation.

"The proposal was received by all embassies in Pyongyang and we are now simply trying to clarify the situation," he said.

"We're deeply concerned by the escalation of tension, which for now is verbal.

"We want to understand the reasons behind this offer."

The latest spike in tensions comes as South Korea deployed two warships with missile defence systems, amid reports that the North has stationed a second missile on its east coast.

Musudan factbox: Alternative names: Mirim, No Dong B, BM-25 First revealed: October 10, 2010 First tested: April 5, 2009 Launch weight: 19,000-26,000 kg Length: 12-19 metres Diameter: 1.5-2 metres Operational range: 3,000-4,000km Launch platform: truck, cargo ship, modified submarine

Yonhap reported that two intermediate Musudan missiles had been transported by train earlier in the week and loaded on vehicles equipped with launch pads, but Seoul says it is not whether the missiles have been moved for a test or for a hostile act.

The Musudan has never been tested, but is believed to have a range of around 3,000 kilometres, which could theoretically be pushed to 4,000 if they were to be given a light payload.

That would cover any target in South Korea and Japan, and possibly even reach US military bases located on the Pacific island of Guam.

A South Korean navy official told Yonhap that two Aegis destroyers with advance radar systems had been deployed - one off the east coast and one off the west coast - to track any missile launch.

Warships deployed: The developments come as South Korea deploys two Aegis warships to track any possible missile launch. ( AFP: Daewoo Shipbuilding & Marine Engineering, file photo )

Missile launch?

Military strength: North v South North Korea South Korea Active troops 1.2 million 655,000 Reserves 5-7.7 million 3 million Tanks 4,100 2,400 Armoured personnel carriers 2,500 2,600 Rocket launchers 5,100 200 Mortars 7,500 6,000 Air defence guns 11,000 300 Combat aircraft 820 (620 serviceable) 460 Helicopters 300 680 Combat vessels 3 19 Submarines 70 23

The United States has urged Pyongyang to stop with the provocations but says it "would not be surprised" if the North launched a missile.

"We've obviously seen the reports that North Korea may be making preparations to launch a missile, and we're monitoring this situation closely," White House spokesman Jay Carney told reporters.

"We would not be surprised to see them take such an action. We have seen them launch missiles in the past ... and it would fit their current pattern of bellicose, unhelpful and unconstructive rhetoric and actions.

"We urge them to stop with the provocations and to focus instead on meeting their international obligations and feeding their own people.

"They are only making themselves more and more isolated from the rest of the world."

The Pentagon has said it will send missile-interceptor batteries to protect its bases on Guam, a US territory some 3,380 kilometres south-east of North Korea and home to 6,000 American military personnel.

Most experts think the North is not yet capable of mounting a nuclear device on a ballistic missile which could strike US bases or territory.

Tensions have soared on the Korean peninsula since December, when the North test-launched a long-range rocket.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 2 minutes 49 seconds 2 m 49 s Korean Australians hope for empty threats Download 1.3 MB

In February, it conducted its third nuclear test and drew fresh United Nations sanctions.

One of North Korea's oldest allies, Fidel Castro, is urging Pyongyang to show restraint.

The former Cuban leader says the North Koreans had demonstrated their technical and scientific advances, and should now step back.

He says the current situation represents one of the greatest risks of nuclear war since the Cuban Missile Crisis five decades ago.

He warns that nuclear war would affect more than 70 per cent of the planet, and both North Korea and its opponents have a duty to avoid that.

ABC/AFP