North Korea's position as a nuclear weapons state will remain undeniable and it will "continue legitimate action" until military threats from the US and its allies are eliminated, state media KCNA said today.

North Korean Foreign Minister Choe Son Hui issued a statement criticising the US and G7 nations.

The G7 foreign ministers condemned the North's April 13 test of what Pyongyang said was a solid-fuel intercontinental ballistic missile and urged denuclearisation at the end of their meeting in Japan on Tuesday.

Tension has flared in recent weeks as the isolated country has ramped up military activities, and threatened "more practical and offensive" action as US and South Korean forces conduct annual springtime military exercises.

North Korea has been reacting furiously to those exercises, calling them a rehearsal for "an all-out, nuclear war."

Choe said North Korea's status as a nuclear power is "final and irreversible," and will remain an "undeniable reality" even if Washington and others in the West deny it.

Pyongyang's development of nuclear weapons was only intended to guard against US threats, she said, urging Washington to drop its "hostile policy" against the North to ensure its own security.

"It is an anachronistic idea if you think that only Washington has the right and capability to carry out a nuclear strike," KCNA quoted her as saying.

"As long as we have the strength to hit back against US nuclear threats, we will never seek recognition or approval from anyone."

Choe accused the G7 countries of illegally interfering in North Korea's internal affairs by demanding denuclearisation, saying Pyongyang will take strong action if they attempt to violate its sovereignty and fundamental interests.

"We will continue all legitimate action granted to any sovereign states until military threats from the US and its allied hostile forces are completely eliminated, and the hostile environment that impedes our independent existence and development is fundamentally ended," Choe said.

- Reuters