* N Korea moves aircraft to strengthen east coast defences - Yonhap
* US bombers flew east of N Korea in show of strength at weekend* China says war will have no winner
North Korea appears to have boosted 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 peninsula.
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 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.
Yonhap suggested the reclusive North was in fact bolstering its defences by moving aircraft to its east coast and taking other measures after US bombers flew close to the Korean peninsula at the weekend.
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.
Ri said on Monday the North's right to 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," he told reporters 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 United States had declared war, calling the suggestion "absurd".
Speaking in Beijing, Chinese Foreign Ministry spokesman Lu Kang said war on the Korean peninsula would have no winner.
"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," Lu told a daily news briefing.
"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."
Risk of miscalculation
US Air Force B-1B Lancer bombers escorted by fighter jets flew east of North Korea in a show of force after a heated exchange of rhetoric between Trump and Kim.
North Korea has been working to develop nuclear-tipped missiles capable of hitting the US mainland, which 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 and 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.
The North 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.
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 Kim in which he called Trump a "mentally deranged US dotard" and said he would tame the US threat with fire.
White House National Security Adviser H.R. McMaster defended Trump's rhetoric and said on Monday he agreed that the risk was that Kim might fail to realise the danger he and his country were facing.
However, McMaster also acknowledged the risks of escalation with any US military option.
"We don't think there's an easy military solution to this problem," said McMaster, who believed any solution would be an international effort.
"There's not a precision strike that solves the problem. There's not a military blockade that can solve the problem," McMaster said.
China, North Korea's sole major ally and largest trading partner, has all along called for calm and dialogue, while world leaders such as UN Secretary-General Antonio Guterres said the only solution to the crisis was a political one.
China's UN Ambassador Liu Jieyi said Beijing wanted the situation "to calm down".
"It's getting too dangerous and it's in nobody's interest," Liu told Reuters in New York.
