Classified documents regarding an alleged British provocation in the Crimean Peninsula which Moscow annexed from Ukraine in 2014 were found by an anonymous source, reported the BBC Sunday.

BBC alleged that the documents contained an assessment of Russia's potential reaction to the passage of the UK warship Defender through the Black Sea.

The PowerPoint presentation featured an Permanent Joint Headquarters (PJHQ) official, asking, "What do we understand about the possible 'welcome party'…?", according to the report.

England's Ministry of Defense said it was aware of the incident.

"The department takes the security of information extremely seriously and an investigation has been launched. The employee concerned reported the loss at the time. It would be inappropriate to comment further," said a spokesman for the agency.

Russia released footage of the incident Wednesday, claiming it had fired warning shots to prevent the vessel from sailing through what it claims as its national waters.

Following the incident, Moscow summoned the British ambassador for a hearing over the alleged provocation.

The UK presented a different version of what took place, calling the encounter a Russian "gunnery exercise," and denying bombs being dropped as further warnings to the ship.

The British Ministry of Defense did, however, confirm the vessel had sailed through "Ukrainian waters," referring to it as an "innocent passage" in accordance with international law.