President Vladimir V. Putin of Russia appeared to acknowledge on Thursday that North Korean troops had been deployed to Russia, commenting for the first time on the assessment of Western officials that the reclusive Asian country had joined Russia’s war effort against Ukraine.

“Images — that is something serious, if there are images they are a reflection of something,” he said, responding to a question about satellite images appearing to show North Korean troops in Russia.

His tongue-in-cheek response, at a conference of emerging-market economies that Russia is hosting, did not explicitly confirm or deny statements made Wednesday by the Pentagon, which said that North Korea had sent troops to Russia.

He was speaking hours after Russia’s lower house of Parliament ratified a mutual defense treaty with North Korea that Mr. Putin had signed with Kim Jong Un, the North’s leader, when Mr. Putin visited Pyongyang in June.

It was a rubber-stamp vote, but Mr. Putin used it to reaffirm Moscow’s ties to North Korea and send a signal that he was drawing in allies who would bolster his standoff with the West.

“Today, we ratified our treaty on strategic partnership which contains article four,” Mr. Putin continued. He was referencing a clause stipulating that should either nation be “put in a state of war by an armed invasion,” the other will “provide military and other assistance with all means in its possession without delay.”