North Korea appears to have boosted defences on its east coast after taking US president Donald Trump's comments on Twitter as a declaration of war.
Tensions have escalated since North Korea conducted its sixth and most powerful nuclear test on September 3, but the rhetoric has reached a new level in recent days with leaders on both sides exchanging threats and insults.
North Korean Foreign Minister Ri Yong Ho said Trump's Twitter comments, in which the US leader said Mr Ri and leader Kim Jong Un "won't be around much longer" if they acted on their threats, amounted to a declaration of war and that Pyongyang had the right to take countermeasures, including shooting down American bomber planes they considered to be flying too close.
On Tuesday, South Korea's Yonhap news agency suggested North Korea was in fact bolstering its defences by moving aircraft to its east coast and taking other measures after US Air Force B-1B Lancer bombers escorted by fighter jets flew east of North Korea in a show of force after the heated exchange of rhetoric between President Trump and Kim Jong-un.
The unverified Yonhap report said the United States appeared to have disclosed the flight route of the bombers intentionally because North Korea seemed to be unaware. South Korea's National Intelligence Service was unable to confirm the report immediately.
Speaking at the United Nations in New York on Monday, Mr Ri said North Korea's right to carry out countermeasures included shooting down US bombers "even when they are not inside the airspace border of our country. The whole world should clearly remember it was the US. who first declared war on our country. The question of who won't be around much longer will be answered then."
White House spokeswoman Sarah Sanders denied the United States had declared war, calling the suggestion "absurd".
Speaking in Beijing, Chinese foreign ministry spokesman Lu Kang said then there would be no winners in any conflict on the Korean peninsula.
"We hope the US and North Korean politicians have sufficient political judgment to realise that resorting to military force will never be a viable way to resolve the peninsula issue and their own concerns," he said. "We also hope that both sides can realise that being bent on assertiveness and provoking each other will only increase the risk of conflict and reduce room for policy manoeuvres. War on the peninsula will have no winner."
However, while China has repeatedly called for dialogue to resolve the issue, it has also signed up for increasingly tough UN sanctions against North Korea.
China's fuel exports to North Korea fell in August, along with iron ore imports, as trade slowed after the latest UN sanctions, but coal shipments resumed after a five-month hiatus, customs data showed on Tuesday.
In Moscow, Russia's foreign ministry said it was working behind the scenes to find a political solution and that using sanctions against North Korea had gone almost as far as it could.
US defence secretary James Mattis, speaking during a visit to India, said he appreciated global efforts to increase pressure on North Korea for its dangerous behaviour.
RISK OF MISCALCULATION
North Korea has been working on developing nuclear-tipped missiles capable of hitting the US mainland, which Mr Trump has said he will never allow.
The United States and South Korea are technically still at war with North Korea after the 1950-53 Korean conflict ended in a truce, not a peace treaty.
The September 3 nuclear test prompted a new round of sanctions on North Korea after the Security Council voted unanimously on a resolution condemning the test.
North Korea says it needs its weapons programmes to guard against US invasion and regularly threatens to destroy the United States, South Korea and Japan. However, the rhetoric has been ratcheted up well beyond normal levels, raising fears that a miscalculation by either side could have massive repercussions.
President Trump's threat last week to totally destroy North Korea, a country of 26 million people, if it threatened the United States or its allies led to an unprecedented direct statement by Mr Kim in which he called Mr Trump a "mentally deranged US dotard" and said he would tame America's threat with fire.
White House National Security Adviser H.R. McMaster defended Mr Trump's rhetoric, saying he agreed that the risk was that Mr Kim might fail to realise the danger he and his country were facing. However, Mr McMaster also acknowledged there was no "easy" military solution.
"There's not a precision strike that solves the problem. There's not a military blockade that can solve the problem," he said.
North Korea has been boosting defences on its east coast, South Korea's Yonhap news agency said on Tuesday, after the North said US president Donald Trump had declared war and that it would shoot down US bombers flying near the Korean peninsula.
Tensions have escalated on the peninsula since Pyongyang conducted its sixth and most powerful nuclear test on September 3, but the rhetoric has reached a new level in recent days with leaders on both sides exchanging threats and insults.
North Korean foreign minister Ri Yong-ho said Trump's Twitter comments, in which the US leader said Mr Ri and leader Kim Jong-un "won't be around much longer" if they acted on their threats, amounted to a declaration of war and that Pyongyang had the right to take counter measures.
Yonhap suggested North Korea was in fact bolstering its defences by moving aircraft to its east coast and taking other measures after US bombers flew close by at the weekend.
The unverified Yonhap report said the US appeared to have disclosed the flight route of the bombers intentionally because North Korea seemed to be unaware. South Korea's National Intelligence Service was unable to confirm the report immediately.
Mr Ri said on Monday the North's right to counter measures included shooting down US bombers "even when they are not inside the airspace border of our country".
"The whole world should clearly remember it was the US who first declared war on our country," he said in New York on Monday, where he had been attending the annual United Nations General Assembly.
"The question of who won't be around much longer will be answered then," he said.
White House spokeswoman Sarah Sanders denied on Monday that the US had declared war, calling the suggestion "absurd".