North Korea is preparing to send as many as 50,000 soldiers to support Russia’s war against Ukraine, Volodymyr Zelensky claimed, a much bigger deployment than anything Pyongyang had committed thus far.

The Ukrainian president said Moscow and Pyongyang had agreed to station between 30,000 and 50,000 North Korean troops on Russian territory, an escalation from earlier deployments that he described as first hundreds and then thousands of men.

Neither Russia nor North Korea confirmed any such agreement, and it was not immediately clear how Ukraine had formulated its assessment.

“North Koreans appear on the territory of the Russian Federation from time to time,” Mr Zelensky said in an interview with the Ukrainian television service United News on Saturday.

“At first, we were talking about hundreds, then thousands, and now a decision has been made for 30,000 to 50,000 North Koreans to be deployed on the territory of Russia.”

Pyongyang is thought to have sent 16,000 soldiers and deminers to Kursk, the Russian region partly seized by Ukrainian forces in 2024, since late that year, along with shipments of ballistic missiles.

The figures Mr Zelensky gave would represent a commitment on a much larger scale. He had said last month that preparations to receive North Korean troops had been underway since June in Voronezh, a region bordering Ukraine.

He said the arrangement would give North Korea something more valuable than the manpower it was sending.

“North Korea will build up its capabilities in fairly modern warfare, will receive licences from Russia and will receive all kinds of military tools from them. We understand this clearly,” he said, adding the troops were gaining combat experience and were not preparing for peaceful circumstances.

Mr Zelensky argued that this made the arrangement a problem for Asia rather than just for Europe, and urged Seoul to work more closely with Kyiv, particularly on air defence, where Ukraine has clear gaps, and on drones.

South Korean law limits what Seoul can supply to countries at war to non-lethal aid.

“They have a legal restriction under their constitution,” Mr Zelensky said of South Korea. “But we would like to have this cooperation and are counting on it. Our diplomats are in contact.”

Mr Zelensky cited Russia’s use of North Korean missiles against Ukrainian targets, including one strike last month that he said killed a family, as evidence of what Pyongyang stood to learn.

Ukraine’s military intelligence agency said last week that North Korea was preparing to send a missile unit of about 90 soldiers to Voronezh with six launchers and 120 missiles to operate as part of Russia’s 112th missile brigade. Andrii Cherniak, a representative of the agency, told Reuters that North Korea had already supplied 40 KN-23 and KN-24 short-range ballistic missiles and Moscow and Pyongyang were expected to settle the details of the deployment at talks next month.

The two countries signed a mutual defence treaty in June 2024, committing each to come to the other’s aid if attacked.

North Korea has since become one of Russia’s most important suppliers of munitions and men, purportedly in exchange for food, fuel, cash and military technology.

Britain, which has trained Ukrainian troops and supplied air defence missiles, has sanctioned a number of North Korean officials over the deployments and joined a group of countries monitoring sanctions enforcement against Pyongyang after Russia vetoed the continuation of a UN panel that previously did the job.