Moscow, Russia - The Kremlin on Thursday dismissed a claim by Seoul that North Korean soldiers were likely to be fighting alongside Russian troops in Ukraine.

"This seems like yet another fake news story," Kremlin spokesperson Dmitry Peskov commented to journalists without elaborating.

Ukraine's Kyiv Post reported Friday that six North Korean military officers had been killed in a Ukrainian missile attack on Russian-occupied territory near Donetsk a day earlier, citing intelligence sources.

South Korean Defense Minister Kim Yong-hyun told lawmakers Tuesday that the report was probably correct.

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"We assess that the occurrence of casualties among North Korean officers and soldiers in Ukraine is highly likely, considering various circumstances," he said.

"The issue of deploying regular troops is highly likely due to the mutual agreements that resemble a military alliance between Russia and North Korea," Kim added.

The head of Ukraine's center for countering disinformation, Lieutenant Andriy Kovalenko, wrote on Telegram Saturday that there were "small numbers of combat engineers" from North Korea in the Donetsk region combat zone.

He said they were monitoring the use of Pyongyang's ammunition, which he said Russia was increasingly dependent upon but is of "low quality," as are North Korean missiles.

Western sources have long said North Korean missiles are being deployed in Ukraine by Russian forces – something both Moscow and Pyongyang have denied.

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South Korea also claims Pyongyang has sent thousands of containers of weapons to Russia for use in Ukraine.

The nuclear-armed North has publicly bolstered military ties with Moscow in recent years. President Vladimir Putin made a rare visit to Pyongyang in June, where he signed a mutual defense agreement with leader Kim Jong Un.

The US and its NATO allies have continued to supply Ukraine with military aid and equipment, which Kyiv has used to strike deep into Russia's territory, stoking fears of nuclear conflict.