Ukrainian officials have released what they say is a questionnaire prepared by Russia's military to ask North Korean soldiers for their uniform sizes and other information.

Ukraine's Centre for Strategic Communication and Information Security, which operates under the Ministry of Culture and Information Policy, posted the questionnaire on social media on Sunday.

The center said the questionnaire has instructions in Russian and North Korean. But the timing of the document's use or how it was obtained has not been disclosed.

Prior to this, the center also released footage purportedly of North Korean soldiers receiving uniforms and equipment in Russia.

The Associated Press quoted the head of the center as saying the footage is the first video evidence of North Korea participating in the war on Russia's side. He called for more support for Ukraine from the international community.

Amid deepening military ties between Russia and North Korea, South Korea's intelligence agency has said the North dispatched about 1,500 special forces troops to Russia's Far East this month. It believes the soldiers will be deployed to the battlefront in Ukraine.