The British Army has confirmed a "breach" of its Twitter and YouTube accounts.
The Ministry of Defence said an investigation is under way after both official sites appeared to have been hacked.
The Army's YouTube channel features videos on cyptocurrency and images of billionaire businessman Elon Musk, while its official Twitter account retweeted a number of posts appearing to relate to crypto assets known as NFTs.
The profile picture on its twitter page was changed numerous times during the hack, and at one point showed a monkey wearing face paint. The bio was replaced with the message: “We all have a dark side. What will yours look like?”
Defence sources would not comment on whether Russians were behind the hack.
Hacking of soldiers’ details has been a feature of the war in Ukraine, with hacker group Anonymous claiming to have released the personal details of 120,000 Russian soldiers fighting in Ukraine in early April.
The British Army cyber attack is the latest hacking incident to affect the organisation. Britain’s computerised army recruitment system closed in mid-March after candidate data was compromised in a possible hack, which resulted in officials deciding to suspend its operations. Data relating to an estimated 120 army recruits was discovered being offered for sale on the dark web.
In 2019, the Army announced it would engage in social media warfare, as it launched a new division of the military dedicated to fighting cyber threats. The purpose of 6 Division (6 Div), is to seek to influence the behaviour of the public and adversaries by specialising in “information warfare”. It is expected to react to social media "attacks" on Britain, and proactively launch similar offensives.
The account was subsequently flooded by a series of retweets encouraging followers to enter competitions to win NFTs - digital artworks that represent real-life assets such as music and videos.
It appeared to take the army about five hours to regain control of its Twitter account.
One senior defence source said they did not believe the hackings would have been a “national security threat”, due to the nature of the platforms.
An Army spokesman said: "We are aware of a breach of the Army's Twitter and YouTube accounts and an investigation is under way.
"We take information security extremely seriously and are resolving the issue. Until the investigation is complete it would be inappropriate to comment further."
It follows a string of high-profile hacks in 2020, when Bill Gates, Elon Musk and Joe Biden’s accounts were taken over by scammers.