Russian President Vladimir Putin appeared to confirm that North Korean troops were in Russia, raising concerns that soldiers had been sent for possible deployment in Ukraine.

The Russian president addressed satellite images released by South Korean intelligence that allegedly showed the soldiers on Russian territory.

“Pictures are a serious matter. If there are images, they reflect something,” he told foreign journalists on Thursday The Washington Post.

Putin also referred to the newly signed security treaty between the two countries, which contains a mutual defense clause.

“As far as our relations with the DPRK are concerned, the treaty was ratified today; it contains Article 4. We have never doubted that the North Korean leadership takes the agreement seriously,” Putin said.

Newsweek contacted the Russian Ministry of Defense by email.

US Defense Secretary Lloyd Austin confirmed on Wednesday that there was evidence of North Korean troops in Russia and said it would be “very, very serious” if they were preparing to fight in Ukraine.

White House spokesman John Kirby added that the U.S. expected at least 3,000 North Korean troops to be trained in Russia and said a deployment against Ukraine was “fair game.”

South Korean intelligence released satellite images last week that appeared to show North Korean troops at a training ground in Russia's Far East.

The agency also told NBC News that it used artificial intelligence facial recognition technology to confirm the sighting of a North Korean soldier in Ukraine.

South Korea's spy service estimates that Pyongyang will send up to 12,000 troops, including special forces, and that most will have arrived in Russia by December.

Ukrainian military intelligence separately claimed that a group of North Korean soldiers had been sent to the Russian border region of Kursk, where Ukraine had carried out a raid.

North Korea previously denied allegations that it had sent its troops to Russia to support the war against Ukraine, calling them “baseless, stereotypical rumors.”

The fight by North Korean troops in Ukraine would be the first foreign war in the country's history.

The Asian country remained one of Russia's few international allies even after the unprovoked invasion of Ukraine in February 2022, continually supplying Russia with key weapons to replenish its dwindling supplies.

On Thursday, South Korean President Yoon Suk Yeol said his government “will not stand idle” if its neighbor sends troops to Russia.

He said this could include a review of the country's long-standing policy of not supplying lethal weapons to countries in conflict.