first declared war on our country," Ri said.

The foreign minister said that North Korea drew this conclusion from the speech US President Donald Trump delivered before the United Nations General Assembly last week.

In that address, Trump said that although the US has great strength and patience, if it is forced to defend itself and its allies "we will have no choice but to totally destroy North Korea."

Ri said that those words were clearly a "declaration of war" against Pyongyang, and he noted that the UN Charter authorises the international body's member states to defend themselves.

He said specifically that all measures were on the table for North Korea to defend itself. On Saturday, during his participation in the top-level debates in the General Assembly, Ri announced that North Koreais in the "final phase" of developing its nuclear arsenal, including ballistic missiles that could potentially deliver nuclear warheads to US territory.

He said, however, that Pyongyang will use atomic weapons only as a "last resort," adding that North Korea has no intention of using or threatening to use nuclear weapons against any country that remains aloof from US military action.

Tensions have been steadily rising since Trump's UN speech, which was delivered in the wake of North Korean missile and nuclear tests, and North Korean leader Kim Jong-un made a rare television appearance calling Trump "mentally deranged," whereupon Trump responded by once again mockingly calling Kim "Rocket man."