North Korea's military has come under the spotlight after the United States joined South Korea and Ukraine this week to accuse Pyongyang of dispatching thousands of troops to Russia, potentially to ready them for combat in the Ukraine war.

North Korea's deployment to Russia to aid its war against Ukraine has the potential to lengthen the already 2-1/2-year old conflict and draw in others, U.S. Defense Secretary Lloyd Austin said on Wednesday.

North Korea said it tested an intercontinental ballistic missile on Thursday, upgrading what it called the "world's most powerful strategic weapon", as Seoul warned Pyongyang could get missile technology from Russia for helping with the war in Ukraine.

North Korea on Thursday launched one of its most powerful missiles, South Korea's military said, Kim Jong Un's first weapons test since being accused of sending soldiers to Russia.

North Korea conducted what appeared to be its longest ever intercontinental ballistic missile test on Thursday as South Korea warned Pyongyang could seek missile technology from Russia in exchange for deploying troops to help with the war in Ukraine.

North Korea on Thursday test-fired one of its most powerful missiles, South Korea's military said, Kim Jong Un's first weapons test since being accused of sending soldiers to Russia.

The United States said Thursday that up to 8,000 North Korean troops have reached Russia's border region with Ukraine trained and ready for combat, as Pyongyang's firing of a long-range missile ramped up tensions days before the US election.