Russian fighter jet almost shot down an unarmed British spy plane last year, according to leaked US military documents

• A Russian fighter jet nearly hit a British spy plane last year, according to leaked US military documents.
• The strike would have had serious implications on NATO member states.

A Russian fighter jet nearly shot down an unarmed British spy plane last September, per leaked US military documents, The Washington Post reported.

The Russian missile was fired off the coast of Crimea, part of Ukraine that Russia has occupied since 2014, and where it has its Black Sea naval fleet.

The incident was mentioned in leaked Pentagon documents that have been widely circulating on social media in recent days.

At the time, UK Defense Minister Ben Wallace called the near miss a "malfunction," adding that Russia had acknowledged the incident occurred over international air space, Reuters reported.

Wallace told British lawmakers that two Russian Su-27 fighter jets had intercepted the RC-135, which is used to collect radio transmissions and other electronic messages, had flown "recklessly," with one plane coming within 15 feet of the aircraft.

Article 5 of NATO's treaty declares that an armed attack against one member state would constitute an attack against all of them, with each state having the right to exercise self-defense against the aggressor.

The leaked document, which is labeled "SECRET/NOFORN" — meaning it cannot be shared with non-US citizens — features other details about Russian interactions with US, British and French surveillance planes up to late February.

Another episode, from December 30, saw a British RC-135 accompanied by two Typhoon fighter jets being intercepted by Russian jets that came within 100 feet of it, per The Post.

The trove of classified US documents leaked last week also features extensive details about Ukraine's military capacities. The leak has been an embarrassment for the Pentagon.

The Department of Defense said on Sunday that it was reviewing the documents to assess how authentic they are.

The Pentagon's deputy press secretary said they had made a formal referral to the Department of Justice to investigate the matter.