North Korea says Trump has declared war

North Korea's Foreign Minister Ri Yong-ho said on Monday that President Donald Trump’s weekend tweet was a declaration of war and Pyongyang had the right to retaliate by shooting down US bombers, even if they are not in its air space.

The White House dismissed the claim as "absurd".

Speaking to reporters outside his New York hotel, Ri responded to Trump, who had warned on Twitter at the weekend that North Korea "won't be around much longer" if it keeps up its threats.

Ri, who attended this year's UN General Assembly session, said the international community had hoped that a "war of words" would "not turn into real actions."

"However, last weekend, Trump claimed our leadership would not be around much longer," Ri said. "He declared a war on our country."

Alarm over Pyongyang's nuclear and ballistic missile programs dominated this year's gathering of world leaders at the United Nations, amid fears the heated rhetoric could accidentally trigger a war.

Those fears were further heightened after US bombers flew off the coast of North Korea on Saturday.

"Since the United States declared war on our country, we will have every right to take counter-measures including the right to shoot down US strategic bombers even when they are not yet inside the airspace border of our country," said Ri.

"The question of who won't be around much longer will be answered then."

TRT World's Ediz Tiyansan reports from New York.

The foreign minister said the statement from Trump was "clearly a declaration of war" even if it came from the US president. Under the US Constitution, Congress is the sole power that can declare war.

The White House disputed Ri's interpretation of Trump's saber rattling.

"We have not declared war against North Korea and frankly the suggestion of that is absurd," said White House spokeswoman Sarah Huckabee Sanders.

Risk of accidental clash

As the rhetoric heated up, South Korea appealed for an easing of tensions, with Foreign Minister Kang Kyung-wha saying that further provocations can be expected from Pyongyang but must not be allowed to get out of control.

"It is imperative that we, Korea and the US together, manage the situation ... in order to prevent further escalation of tensions or any kind of accidental military clashes which can quickly go out of control," Kang said in Washington.

South Korea has reacted with unease to Trump's threat to "totally destroy" North Korea as its densely populated capital Seoul is located just 35 miles from the demilitarized zone separating the Korean peninsula.