Russian Foreign Minister Sergei Lavrov warned today against heating up the North Korea crisis with military manoeuvres, but stressed that Moscow and Washington had a common stand.

"On North Korea we have no differences with the United States," Lavrov told journalists as he met with US Secretary of State John Kerry for talks on the sidelines of a meeting of G8 foreign ministers in London.

"One just shouldn't scare anyone with military manoeuvres and there's a chance that everything will calm down," he added in Russian, without specifying which countries he believed were carrying out such militarised exercises.

South Korean and US forces raised their alert status to "vital threat" today before an expected North Korean missile test, with tensions wound tight during a five-day build-up to a key anniversary.

The North last week told foreign diplomats in Pyongyang they had until Wednesday to consider evacuation, fuelling speculation of a launch between now and the April 15 birthday celebrations for late founder Kim Il-Sung.

Any launch could coincide with visits by Kerry and NATO chief Anders Fogh Rasmussen, who will both be in Seoul on Friday.