WASHINGTON, April 8 (New York Times) - Secret documents that provide details of US and NATO plans to help prepare Ukraine for a spring offensive against Russia have spilled onto social media platforms, the New York Times reported.

The apparent leak looked like a Russian disinformation operation to sow doubt about Ukraine’s planned counteroffensive, a Ukrainian presidential official said on Friday.

Mykhailo Podolyak told Reuters news agency the data contained a “very large amount of fictitious information” and Russia was trying to seize back the initiative in its invasion.

The Pentagon said on Thursday it is assessing the apparent security breach.

“We are aware of the reports of social media posts, and the department is reviewing the matter,” Deputy Press Secretary Sabrina Singh said.

The documents were spread on Twitter and Telegram, and reportedly contain charts and details about weapons deliveries, battalion strengths and other sensitive information, the Times said.

There was no explanation as to how the plans were obtained.

Information in the documents is at least five weeks old with the most recent dated March 1, the report said. The plans did not provide specific action such as when Ukraine would launch the offensive.