North Korea on Thursday tested an upgraded intercontinental ballistic missile (ICBM) that demonstrated what it said is the "world's most powerful strategic deterrent," in Pyongyang's first weapons test since being accused of dispatching troops to Russia.

Leader Kim Jong Un, who oversaw the launch, said it was a warning to his country's enemies and vowed that the North "will never change its line of bolstering up its nuclear forces."

"The test-fire is an appropriate military action that fully meets the purpose of informing the rivals, who have intentionally escalated the regional situation and posed a threat to the security of our Republic recently, of our counteraction will," he was quoted by the North's official Korean Central News Agency as saying in a rare same-day report covering the launch.