Pyongyang, North Korea - South Korea's spy agency has revealed that 1,500 North Korean soldiers have been sent to Russia for deployment in Ukraine. In response, Kyiv is calling on them to lay down their arms.

Pyongyang has sent an additional 1,500 soldiers to Russia, pushing the total number of deployed North Korean soldiers up to 3,000, with numbers expected to reach 10,000 by the end of the year.

The revelations came from a report provided to South Korean lawmakers by Seoul's spy agency on Wednesday. Just last week, Seoul had warned of a "large-scale" deployment of North Korean troops to Russia.

According to Park Sun-won, a representative for South Korea's Democratic Party, the spy agency revealed that the soldiers had been transported inside of Russia but were yet to be deployed on the Russian frontline in Ukraine.

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"Signs of troops being trained inside North Korea were detected in September and October," Park Sun-won said after the briefing, Reuters reports.

"It appears that the troops have now been dispersed to multiple training facilities in Russia and are adapting to the local environment."

On Wednesday, US Defense Secretary Lloyd Austin revealed that there was evidence that Pyongyang had already sent troops to Russia.

"What exactly they're doing is left to be seen. But, yes, there is evidence that there are DPRK troops in Russia," he said.

In response to reports that North Korean soldiers have been sent to Russia by Pyongyang, Ukrainian officials have sent out a stark message.

"We address fighters of the Korean People's Army who were sent to help Putin's regime," the AFP cites Kyiv's military intelligence as saying.

"You must not die senselessly in a foreign land. You must not repeat the fate of hundreds of thousands of Russian soldiers who will never return home!"