The hacked website carried a message that reportedly read: "This is a threat. Isis is in Argentina and you will hear from us soon." Reuters reported that the website also displayed images of people dressed in black, which were on view for around 20 minutes, before the Argentine army took down the website.
A message on the site apologises to visitors for the inaccessibility, informing them that the site is "temporarily under maintenance".
Argentine army spokeswoman Dolores San Martin said the army was investigating the cyberattack. However, the identity of the hackers remains unclear. The websites of Argentina's air force and navy were not affected by the attack.
Pro-Isis hackers have previously claimed to have hacked various international government agencies and attempted to spread fear by publishing "kill lists". However, security experts have said that the extremist group's so-called hackers are unskilled and unsophisticated. Experts also warned of the likelihood of pro-Isis low-level script kiddies evolving over time to pose serious threats.