Ukrainian prosecutors said on Friday they had launched an investigation into North Korea's support for Russia in the war as a possible crime of aggression.
By arming and supplying ground forces engaged in fighting against Ukraine, North Korean officials could face charges, the Prosecutor General's Office told Reuters.
"We are documenting and collecting evidence of all possible aspects of such involvement as part of the core proceeding on the crime of aggression," the office said in a statement.
Aspects of the alleged crime include supplying arms to the Russian Federation, organising training for Russian military personnel and direct participation by North Korean forces in hostilities, it said.
Ukraine's military intelligence agency, South Korea and several Western governments have said that North Korean troops trained in Russia have been deployed in the Kursk region, a Russian border area where Ukrainian forces staged a major incursion in August.
The Kremlin has previously dismissed reports about the North's troop deployment as "fake news". But Russian President Vladimir Putin, asked about the issue on Thursday, did not directly deny that North Korean troops were in Russia.
The Ukrainian intelligence agency has said a total of around 12,000 North Korean troops, including 500 officers and three generals, were already in Russia, and training was taking place on five military bases.
On Friday, the Dutch Defence Ministry said its intelligence confirmed at least 1,500 North Korean troops were expected to be deployed in the short term to assist Russia's combat operations against Ukraine.
