North Korean state media today warned of a nuclear attack on the US at any sign of a US pre-emptive strike, as a US Navy strike group led by a nuclear-powered aircraft headed towards western Pacific.
Tension had increased in the Korean peninsula with talk of military action by the US gaining traction after its strikes last week against Syria and as concerns mount over the prospect of North Korea conducting a sixth nuclear test soon.
According to North Korea's official Rodong Sinmun newspaper, the country was prepared to respond to any aggression by the US.
"Our revolutionary strong army is keenly watching every move by enemy elements with our nuclear sight focused on the U.S. invasionary bases not only in South Korea and the Pacific operation theatre but also in the U.S. mainland," it said.
South Korean acting president Hwang Kyo-ahn warning of "greater provocations" by North Korea had ordered the military to intensify monitoring and to ensure close communication with the US.
"It is possible the North may wage greater provocations such as a nuclear test timed with various anniversaries including the Supreme People's Assembly," said Hwang, acting leader who took office after president Park Geun-hye was removed amid a graft scandal.
Meanwhile, MI6 head Sir John Sawers had warned that tensions with North Korea were actually a much bigger threat to world peace than the war in Syria.
''If you are looking for a world crisis which could bring about the dangers of a clash between great powers then North Korea is a bigger concern than Syria,'' he told BBC Four's Today programme.
According to commentators, the show of force by the US masked the fact the US had limited options in dealing with North Korea because as missile strike could escalate to nuclear war.