The Pentagon is investigating what appear to be screenshots of classified US and NATO military information about Ukraine circulating on social media, a Pentagon official told CNN.

CNN has reviewed some of the images circulating on Twitter and Telegram but is unable to verify if they are authentic or have been doctored.

Pentagon deputy press secretary Sabrina Singh would not weigh in on the documents’ legitimacy but said in a statement that the Defense Department is “aware of the reports of social media posts, and the Department is reviewing the matter.”

Mykhailo Podolyak, the adviser to the head of the Office of the President of Ukraine, said on his Telegram channel he believes the Russians are behind the purported leak. Podolyak said the documents that were disseminated are inauthentic, have “nothing to do with Ukraine’s real plans” and are based on “a large amount of fictitious information.”

The emergence of the documents, whether genuine or not, has heightened focus on when the planned Ukrainian counteroffensive will begin and what, if anything, either side knows about the other’s preparations for it.

One image that has been circulating on Russian Telegram channels and was reviewed by CNN is a photo of a hard copy of a document titled “US, Allied & Partner UAF Combat Power Build.”

Another is titled “Russia/Ukraine Joint Staff J3/4/5 Daily Update (D+370).” J3 refers to the operations directorate of the US military’s joint staff, J4 deals with logistics and engineering, and J5 proposes strategies, plans and policy recommendations.

The New York Times, which first disclosed the Pentagon investigation, reported that some of the images circulating online describe intelligence that could be useful to Russia, such as how quickly the Ukrainians are expending munitions used in US-provided rocket-systems.

Podolyak called the documents “a bluff, dust in your eyes” and said that “if Russia really did receive real scenario preparations, it would hardly make them public.”

“Russia is looking for any way to seize the information initiative, to try to influence the scenario plans for Ukraine’s counteroffensive,” he said. “To raise doubts, compromise previous ideas and frighten with their ‘awareness.’ But these are just standard elements of the Russian intelligence’s operational game and nothing more. It has nothing to do with Ukraine’s real plans.”

Podolyak added that Russian troops “will get acquainted” with Ukraine’s real counteroffensive plans “very soon.”

Asked about the images circulating on Twitter and Telegram, Kremlin spokesperson Dmitry Peskov told CNN in a statement that “we don’t have the slightest doubt about direct or indirect involvement of the United States and NATO in the conflict between Russia and Ukraine.”

“This level of involvement is rising, is rising gradually,” he said. “We keep our eye on this process. Well, of course, it makes the whole story more complicated, but it cannot influence the final outcome of the special operation.”