Investigation launched into 'leaked secret NATO plans' for war in Ukraine

Secret documents disclosing efforts by US, the UK and other NATO allies to build up Ukraine's forces ahead of a new offensive against Russian troops appear to have been leaked online.

The US defence department is investigating who is responsible for the potentially damaging leak, which comprised screenshots of classified military documents posted on Twitter and Telegram.

The New York Times, which first reported the breach, quoted military analysts as saying the files appear to have been modified in certain parts, which could point to an attempt by Moscow to spread disinformation.

A Wall Street Journal correspondent noted that Russian propaganda channels appeared to have photoshopped at least one of the documents after the original ones were posted. 

Yaroslav Trofimov noted how there was suddenly a significant increase in the number of Ukrainian casualties and equipment losses recorded and a massive decrease in the Russian battle damage.

The act of stealing secret documents and leaking them, either with or without modifications, is a long-standing weapon of information warfare designed to undermine an opponent.

It would benefit Russia for information about Ukraine’s battle plans and Western support to be leaked online.

The classified files - including one marked "top secret" and another marked "secret" - are dated from late February and early March.

They do not reveal specific dates or details about Ukraine's anticipated spring offensive in the east and south of the country.

But they do offer clues about the kind of military formations that Western allies are helping their Ukrainian partners build up.

The New York Times said US officials were trying to have the files taken down off the social media sites.

However, as of this morning, versions of the leaks were still being widely shared.