North Korea has dismissed warnings by US President Donald Trump that it would face "fire and fury" if it threatened the United States as a "load of nonsense" and outlined detailed plans on for a missile strike near the US Pacific territory of Guam.
Experts in South Korea said the plans unveiled by Pyongyang ratcheted up risks significantly, since Washington was likely to view any missile aimed at its territory as a provocation, even if launched as a test.
North Korea's apparently rapid progress in developing nuclear weapons and missiles capable of reaching the US mainland has fuelled tensions that erupted into a war of words between Washington and Pyongyang this week, unnerving regional powers and global investors.
Asian stocks fell, with shares in Seoul slumping to a 7-week low, after North Korea said it was finalising plans to fire four intermediate-range missiles over Japan to land 30-40km from Guam, adding detail to a plan first announced on Wednesday.
European shares also opened weaker.
Guam, more than 3000km to the southeast of North Korea, is home to about 163,000 people and a US Navy installation that includes a submarine squadron, a Coast Guard group and an air base.
As announced by North Korea, the planned path of the missiles would cross some of the world's busiest sea and air traffic routes.
The North Korean army would complete its plans in mid-August, ready for leader Kim Jong Un's order, state-run KCNA news agency reported, citing General Kim Rak Gyom, commander of the Strategic Force of the Korean People's Army.
"The Hwasong-12 rockets to be launched by the KPA (Korean People's Army) will cross the sky above Shimane, Hiroshima and Koichi Prefectures of Japan," the report said. "They will fly 3356.7 km for 1,065 seconds and hit the waters 30 to 40 km away from Guam."
While North Korea regularly threatens to destroy the US and its allies, the report was unusual in its detail. It follows two successful tests of an intercontinental missile by the isolated state in July and a series of other missile tests.
"Even if the North's missiles do not hit the ocean territory of Guam, the US will not tolerate such a provocation simply because it is a severe threat to its national security," said Cha Do-hyeogn, visiting researcher at the Asian Institute for Policy Studies in Seoul.
Masao Okonogi, professor emeritus at Japan's Keio University, said before the latest KCNA report that Pyongyang may be issuing a warning or advance notice of changes to its missile testing program rather than threatening an attack.
Major airlines which fly over the region said they had so far made no plans to change flight paths.
"Sound dialogue is not possible with such a guy bereft of reason and only absolute force can work on him," KCNA said of Trump. Trump had said on Tuesday that any threats by North Korea would be "met with fire and fury like the world has never seen".
Guam Governor Eddie Calvo said there was no heightened threat from North Korea.
The US Seventh Fleet currently has six Aegis ballistic missile defence ships in the region capable of targeting North Korean missiles, and Japan has a further four. Guam also has a Terminal High Altitude Area Defense (THAAD) anti-missile system, similar to one recently installed in South Korea.
The United States and South Korea remain technically still at war with North Korea after the 1950-53 Korean conflict ended with a truce, not a peace treaty.
US Defense Secretary Jim Mattis issued a stark warning on Wednesday, telling Pyongyang it would lose any arms race or conflict.
"The DPRK should cease any consideration of actions that would lead to the end of its regime and the destruction of its people," Mattis said in a statement, using the initials for North Korea's official name, the Democratic People's Republic of Korea.