Ukrainian President Volodymyr Zelenskyy says he has agreed with South Korean President Yoon Suk-yeol to strengthen cooperation between their countries in light of North Korea's dispatch of its troops to Russia.

Zelenskyy said on social media on Tuesday that he had a call with Yoon and discussed the involvement of North Korean military forces in Russia's invasion of Ukraine.

He said, "The conclusion is clear -- this war is becoming internationalized, extending beyond two countries."

Zelenskyy said he shared recent data with Yoon on the deployment of 3,000 North Korean troops to Russian training grounds near the combat zone, with their number expected to increase to approximately 12,000.

The Ukrainian president added that the two leaders "agreed to strengthen intelligence and expertise exchange" to "develop an action strategy and countermeasures to address this escalation."

He said the two countries "will soon exchange delegations to coordinate actions."

South Korea's presidential office said that Yoon told Zelenskyy during the phone talks that North Korea is taking unprecedented and dangerous steps by deploying special forces to Russia.

Yoon also reportedly conveyed his intention to strengthen bilateral cooperation with measures including close communication between Seoul and Kyiv through exchanges of delegations.