via BBC:
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 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).
The document does not say where the forces are located or what they are doing.
The numbers of personnel may be small, and will doubtless fluctuate. But special forces are by their very nature highly effective. Their presence in Ukraine is likely to be seized upon by Moscow, which has in recent months argued that it is not just confronting Ukraine, but Nato as well.