North Korea ready to 'counter-attack' in face of US 'provocation'

North Korea is ready to "counter-attack" in the face of ongoing "provocation" from the United States, its foreign minister has said amid a spike in tension caused by Pyongyang's latest nuclear test.

"The Korean people have indicated that we are ready to wage a counter-attack against provocation by enemies," Foreign Minister Ri Yong-Ho said yesterday at a meeting of the Non-Aligned Movement in Venezuela.

The warning comes after two US supersonic bombers flew over South Korea on Tuesday in a show of force following North Korea's fifth and largest-ever nuclear test last week.

Ri said the nuclear tests were needed to counter "threats" from Washington.

"It was inevitable that the Democratic People's Republic of Korea would use the option of nuclear armament after having done everything to safeguard national security in view of constant threats from the United States," he said through an interpreter.

He called nuclear tests part of a "legitimate" defence policy to counter US military exercises on the peninsula.

US troops have been present in South Korea since the Korean War (1950-1953), which ended in an armistice rather than a peace treaty -- meaning the two neighbours technically remain at war.

Currently, South Korea hosts some 28,000 US troops.