Russian military bloggers have expressed concern over allegedly secret documents about Ukraine’s military actions that recently leaked online, underscoring fears of a future counteroffensive, the Institute for the Study of War said in its latest update.

“While several prominent Russian military bloggers immediately dismissed the authenticity of the documents and suggested they were forged, they focused on the possibility that the published documents were disinformation designed to mislead the Russian military command,” he wrote to ISW.

ISW suggested that the New York Times article detailing US and NATO plans to support Ukraine “exposed a significant sore spot in the Russian information space,” Kyiv Independent quotes.

The Pentagon has begun an investigation into who may have leaked the documents published on Twitter and Telegram, the New York Times reports.

The five-week-old documents do not reveal when, how and where Ukraine plans to launch a counteroffensive. According to military analysts, the documents were probably forged from their original format, which reduced the number of losses on the Russian side and increased the losses on the Ukrainian side.

Analysts told the NYT that the changes to the document may be part of a Russian disinformation campaign. However, the leak is a “significant violation of US intelligence efforts to help Ukraine,” the NYT writes.

Ukrainian special services called the documents fake.

“The most successful operations of the Russian special services in recent decades took place in Photoshop,” Andriy Yusov, spokesman for the Main Intelligence Directorate of the Ministry of Defense of Ukraine, told the National Television.