The protest group used the broadcaster's text messaging service to send out fake news alerts, including a headline claiming there had been an assassination attempt on Qatar's prime minister.
The news network released the following statement on its website: "The message claiming that [Qatar]'s prime minister has been the target of an assassination attempt… is false and was a result of a hack."
Pro-Syrian movement the Syrian Electronic Army (SEA) has claimed responsibility for the security breach, targeting the broadcaster over its coverage of the rebellion against Syrian president Bashar al-Assad's regime.
This is the fourth time that Al Jazeera has been on the receiving end of a cyber attack since hostilities in Syria intensified. Last week, its website was breached and emblazoned with a Syrian flag by a group calling itself al-Rashedon.
The SEA previously claimed it was behind hacks on Al Jazeera's English website and Twitter account.
Last week, a Twitter account operated by Reuters was hacked by pro-Syrian activists.