North Korea has warned it is prepared to sink an American aircraft carrier, as Japanese navy vessels joined a US "armada" for exercises in the western Pacific.
The USS Carl Vinson carrier strike group was ordered to head towards the Korean Peninsula as tensions rose over Pyongyang's nuclear and missile ambitions.
US vice-president Mike Pence has said it should arrive "within days" after it carried out a short training exercise with Australian forces.
:: 'Armada' was heading wrong way
"Our revolutionary forces are combat-ready to sink a US nuclear powered aircraft carrier with a single strike," the Rodong Sinmun, the newspaper of the North's ruling Workers' Party, said in a commentary.
It added that the strike would be "an actual example to show our military's force" and called the aircraft carrier a "gross animal".
The remarks on page three of the paper came after a two-page feature about leader Kim Jong-Un's visit to a pig farm.
Two Japan Maritime Self-Defense Force destroyers left Sasebo port in southern Japan on Friday to join the USS Carl Vinson strike group, which also includes a guided-missile cruiser and a guided-missile destroyer.
The joint exercises, which have been described as "routine" by Tokyo, were expected to last several days.
North Korea further raised tensions with the arrest of a Korean-American at Pyongyang airport as he attempted to leave the country.
Tony Kim had been teaching accounting at the Pyongyang University of Science and Technology for a month.
Pyongyang has warned it will respond to any US aggression and has threatened to lay waste to South Korea and Japan.
North Korea has also threatened a nuclear strike on Canberra after urging Australia to think twice before "blindly and zealously toeing the US line".
"If Australia persists in following the US' moves to isolate and stifle North Korea... this will be a suicidal act," a North Korean foreign ministry spokesman said after Mr Pence's visit to Australia.
Australia's foreign minister, Julie Bishop, responded by saying the North Korean government "should invest in the welfare of its long-suffering citizens, rather than weapons of mass destruction".
China's foreign minister appealed for calm during a visit to Greece.
"We need to issue peaceful and rational sounds," Wang Yi said.