The UK is among a number of countries with military special forces operating inside Ukraine, according to one of dozens of documents leaked online.
It confirms what has been the subject of quiet speculation for over a year.
The leaked files, some marked "top secret", paint a detailed picture of the war in Ukraine, including sensitive details of Ukraine's preparations for a spring counter-offensive.
The US government says it is investigating the source of the leak.
According to the document, dated 23 March, the UK has the largest contingent of special forces in Ukraine (50), followed by fellow Nato states Latvia (17), France (15), the US (14) and the Netherlands (1).
Source:
Yahoo News