South Korea and Japan have reported that North Korea fired an intercontinental ballistic missile, recording the longest flight ever before landing in waters near the east coast.

After observing the launch, Kim Jong-un took to state media to warn Pyongyang’s international opponents of his willingness to respond to threats and take “appropriate military measures.”

The North Korean leader continued by stating that his country “will never change its line of strengthening its nuclear forces.”

The ICBM flew for approximately 86 minutes and was reportedly fired at a steep angle, according to Japanese Defense Minister General Nakatani. The increase in duration is concerning for those concerned, as the increase in flight time could be a result of improvements made since the last launch.

South Korea’s Joint Chiefs of Staff have since said that the angle could have been an attempt to avoid neighboring countries and that the missile could have covered a much greater distance if it had been fired horizontally.

Jung Chang Wook, head of the Korea Defense Studies Forum think tank in Seoul, told the AP that the missile launched Thursday could have carried the country’s largest and most destructive warhead.

Is Pyongyang warming up?

The violation of UN Security Council resolutions came at a time when relations between North Korea and its peninsular neighbor remain tense. Earlier this month, it was reported that North Korea had destroyed the last remaining connecting roads between the two countries in an aggressive move.

The launch was likely a means to attract international attention, as South Korea had warned of a potential intercontinental ballistic missile this week ahead of the Nov. 5 U.S. presidential election.

The country has previously argued that advancing its nuclear program is the only reasonable response to the continued expansion of the US-South Korea military alliance that may strike. Both countries have denied such accusations.

Responding to the launch, White House National Security Council spokesman Sean Savett said the country “continues to prioritize its illegal weapons of mass destruction and ballistic missile programs over the well-being of its people.”

There have been continued concerns that Pyongyang may be seeking Russian support to expand its nuclear program, especially given the recent troop dispatch to support Vladimir Putin’s forces in the current conflict with Ukraine.

He US Pentagon has now estimated that approximately 10,000 troops have been sent to eastern Russia, some to the Kursk region and there is still more to deploy.

No country has confirmed the accusations.

Following the recent launch, South Korean and US officials issued a statement saying they would “take strong and varied response measures.” Seoul has said new sanctions will be imposed over the intercontinental ballistic missile.