North Korea is expanding a weapons plant that manufactures missiles used by Russia against Ukraine, according to new research from a US-based think tank.

North Korean leader Kim Jong-un has visited the facility several times and the state media has previously talked about the tactile missiles being mass-produced at the location.

Technical advisors from North Korea have arrived in Russian-controlled Mariupol, Ukrainian sources told CNN. Soldiers from Kim Jong Un's army were also spotted in Kharkiv. Ukrainian sources told CNN that technical advisors from North Korea have arrived in Mariupol,