Ukrainian President Volodymyr Zelensky blasted what he called his allies' "zero" response to Russia's deployment of North Korean troops for the war in Ukraine, saying on Thursday a weak reaction would encourage Russia's Volodymyr Putin to beef up the contingent.

Axar.az reports that the Ukrainian leader, in an interview with South Korea's KBS television channel, said he believed Moscow was already trying to agree for North Korea to send engineering troops and a "large number of civilians" to work at Russian military plants.

"Putin is checking the reaction of the West ... And I believe that after all these reactions, Putin will decide and increase the contingent ... The reaction that is there today is nothing, it is zero," Zelensky said.

He began publicly warning of North Korean involvement in the war on Oct. 13. Western allies have since described the move as a major escalation, but have not announced retaliatory measures or said they are preparing to implement any.

South Korea has offered intelligence assistance and wider cooperation on the matter, and it is considering sending a team of military monitors to Ukraine, according to South Korean officials.

In prepared remarks to the U.N. Security Council on Wednesday, Ukraine's delegation named three North Korean generals it says are accompanying thousands of Korean People's Army troops deployed to Russia in aid of Moscow's war in Ukraine.