An investigation is under way after both official sites appeared to have been hacked.
The Army's YouTube channel featured videos on cyptocurrency and images of billionaire businessman Elon Musk.
The official Twitter account had retweeted a number of posts appearing to relate to NFTs.
NFT stands for non-fungible token. An NFT is a distinct cryptographic token that cannot be replicated, which acts as a certificate of ownership for virtual items.
At one stage, the account name was changed to Bapesclan and the profile picture was an ape-like cartoon figure in clownish make-up.
The Twitter account was restored to normal by Sunday evening.
A tweet posted afterwards read: "Apologies for the temporary interruption to our feed. We will conduct a full investigation and learn from this incident. Thanks for following us and normal service will now resume."
The YouTube account also appeared to have its usual videos restored.
An Army spokesperson 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."
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