Ukrainian President Volodymyr Zelenskyy has said up to 50,000 North ​Korean soldiers will be deployed in Russia to fight for Pyongyang’s ally, while calling on South Korea to provide support for its air defense.

Zelenskyy said on X on Saturday that “a decision has been made for 30,000 ⁠to 50,000 North Koreans to be deployed on the territory of Russia,” a higher figure than his estimate of 30,000 in July. He did not elaborate on how he obtained the information.

He said Kyiv had found some North Korean missiles in Ukraine’s territory, without disclosing their locations.

“It ⁠is absolutely clear that North Korea will ​continue ⁠to build its experience in modern warfare, receive licenses from Russia, and receive all kinds of military tools from them,” he said.

Urging Seoul to have ⁠closer cooperation with Kyiv, Zelenskyy said that Ukraine “would very much like to receive ​support ⁠from South Korea in an area where ‌we have a shortage,” referring to its air defense systems.

“We are ready to work on the drone deal and other areas as well,” he said, adding that ‌Ukrainian diplomats “are in contact” with Seoul to push potential ‌deals.

Russian President Vladimir Putin and North Korean leader Kim signed a comprehensive strategic partnership treaty during Putin’s June 2024 visit to Pyongyang. The pact includes a mutual assistance provision if either country faces external aggression.

North ⁠Korea has cast its deployment as assistance to a treaty partner.

North Korea sent an estimated 14,000 soldiers to Russia’s Kursk Region in 2024, helping Moscow beat back a major incursion into the region by Ukrainian forces.

This month, an official at Ukraine’s military intelligence told Reuters that a North Korean missile unit has begun deploying to western Russia and could be equipped with 120 ballistic missiles and six ‌launchers for strikes against Ukraine.

Ukraine is very short of high-end air defenses, ​and Russia has tried to exploit this by using more ballistic missiles, which ‌are particularly hard to shoot ⁠down.

North Korea has supplied Russia with millions of artillery and mortar rounds, ballistic ⁠missiles, long-range artillery and multiple-launch rocket systems, according to Ukrainian and independent assessments.

The North Korean Embassy in Russia ‌did not immediately respond ​to a request from Reuters for a ‌comment.

South Korea’s Foreign Ministry did not ​respond to a request from Reuters for a comment outside business hours.