The EU has confirmed it is "actively investigating" a potential breach of its diplomatic communications network, following reports that secret cables had been stolen by hackers.
Thousands of cables from the network were compromised over a three-year period according to The New York Times, which has published a selection of them.
The cables reveal the EU's concerns about the US administration under President Trump, and his ability to deal with China and Russia.
:: They describe the Helsinki summit between the American and Russian presidents as "successful (at least for Putin)".
:: They show that Chinese premier Xi Jinping claimed "the US was behaving as if it was fighting in a no-rules freestyle boxing match".
:: They reveal Ukrainian fears that Crimea had become "a 'hot-zone' where nuclear warheads might have already been deployed".
A spokesperson for the European Council did not deny the authenticity of the cables to Sky News.
They stated: "The Council Secretariat is aware of allegations regarding a potential leak of sensitive information and is actively investigating the issue.
"The Council Secretariat does not comment on allegations nor on matters relating to operational security. The Council Secretariat takes the security of its facilities, including its IT systems."
Security firm Area 1 discovered the cables because they were posted to an open internet site which the attackers set up during the course of the attack.
The hackers are also believed to have compromised the communications networks of the United Nations, as well as various foreign affairs ministries.
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According to The New York Times, the techniques used to steal the cables followed the established procedures of People's Liberation Army (PLA) Unit 61398 – an elite hacking organisation within the Chinese military.
Security experts have urged caution regarding any attribution of the attack however, as threat actors are increasingly learning to copy each other's tactics in order to misdirect investigators.