The Ministry of Defence is investigating whether a brawl between British soldiers and locals in Latvia was set up by Russia to discredit UK military forces in the Baltic state.
The incident occurred when two members of the Grenadier Guards were eating in a McDonalds eaterie in Riga and were set upon by locals.
A TV crew was positioned to film the brawl, and a Latvian with the soldiers followed the crew and saw them enter the offices of a pro-Russian media outlet.
A defence source told The Telegraph: "Our assessment is that this is clearly a set-up: 'Let's go and make these guys look like thugs and film it.'"
It comes after MI5 director Andrew Parker in a rare interview warned that Russia had adopted an "increasingly aggressive" approach to spying and subversion.
He said Russia was "using its whole range of state organs and powers to push its foreign policy abroad in increasingly aggressive ways – involving propaganda, espionage, subversion and cyberattacks."
Britain has clashed in recent years with Russia over the alleged assassination of dissident Alexander Litvinenko in London in 2006 by Russian security forces, and the Ukraine crisis. In recent months tensions have escalated further over Russia's bombing of Aleppo in Syria.
A spokesman for the army said: "We are aware of an incident involving two soldiers in Riga. The circumstances are being investigated and it would be inappropriate to comment further at this time."
The incident came at the end of a fortnight-long training deployment to the Nato member state.
In October, Defence Secretary Michael Fallon announced that Britain would send troops to Estonia, as part of a permanent Nato deployment to Nato states bordering Russia.