NATO has launched an investigation into the impact of a data breach of classified military documents being sold by a hacker group online.

According to the BBC, the data includes blueprints of weapons being used by Nato allies in the Ukraine conflict.

A report suggests criminal hackers are selling dossiers after stealing data linked to a major European weapons maker, MBDA Missile Systems.

The company admitted its data was among the stash but claimed none of the classified files belong to the firm.

The firm, based in France, said its information was hacked from a compromised external hard drive, adding that it was cooperating with authorities in Italy, where the data breach took place.

NATO investigations are centred around one of MBDA’s suppliers.

A Nato spokesman said: “We are assessing claims relating to data allegedly stolen from MBDA. We have no indication that any Nato network has been compromised.”

The BBC said: “Cyber criminals, operating on Russian and English forums, are selling 80GB of the stolen data for 15 Bitcoins (approximately £273,000) and claimed to have sold the stash to at least one unknown buyer so far.”