We will wipe out US, allies

North Korean state media warned the United States of a "super-mighty preemptive strike" after US Secretary of State Rex Tillerson said the United States was looking at ways to bring pressure to bear on North Korea over its nuclear programme.

US President Donald Trump has taken a hard line with North Korean leader Kim Jong Un, who has rebuffed admonitions from sole major ally China and proceeded with nuclear and missile programmes in defiance of UN Security Council sanctions.

The Rodong Sinmun, the official newspaper of the North's ruling Workers' Party, did not mince its words. "In the case of our super-mighty preemptive strike being launched, it will completely and immediately wipe out not only US 'imperialists' invasion forces in South Korea and its surrounding areas but the US mainland and reduce them to ashes," it said.

Reclusive North Korea regularly threatens to destroy Japan, South Korea and the United States and has shown no let-up in its belligerence after a failed missile test on Sunday, a day after putting on a huge display of missiles at a parade in Pyongyang.

"We're reviewing all the status of North Korea, both in terms of state sponsorship of terrorism as well as the other ways in which we can bring pressure on the regime in Pyongyang to re-engage with us, but re-engage with us on a different footing than past talks have been held," Tillerson told reporters in Washington on Wednesday.

US Vice President Mike Pence, on a tour of Asian allies, has said repeatedly an "era of strategic patience" with North Korea is over.

US House of Representatives Speaker Paul Ryan said during a visit to London the military option must be part of the pressure brought to bear.

North and South Korea are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty.

South Korea's acting president, Hwang Kyo-ahn, at a meeting with top officials yesterday, repeatedly called for the military and security ministries to maintain vigilance.

The defence ministry said US and South Korean air forces were conducting an annual training exercise, codenamed Max Thunder, until April 28. North Korea routinely labels such exercises preparations for invasion.

The North has said it has developed a missile that can strike the mainland United States, but officials and experts believe it is some time away from mastering the necessary technology, including miniaturising a nuclear warhead.

Meanwhile, the United States and Russia clashed at the United Nations on Wednesday over a US-drafted Security Council statement to condemn North Korea's latest failed ballistic missile test.  Diplomats said China had agreed to the statement. Such statements by the 15-member council have to be agreed by consensus.

There has been some confusion over the whereabouts of a US aircraft carrier group after Trump said last week he had sent an "armada" as a warning to North Korea, even as the ships were still far from Korean waters.

The US military's Pacific Command explained that the USS Carl Vinson strike group first had to complete a shorter-than-planned period of training with Australia. It was now heading for the Western Pacific as ordered, it said.