The mobile service of Qatar-based news network al-Jazeera Arabic has been hacked.
Three texts with fake news alerts were sent via the broadcaster's SMS service.
A breaking news statement on the site said "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".
A pro-Syrian group calling itself the Syrian Electronic Army (SEA) claimed responsibility for the attack.
"We'd like to inform our subscribers that al-Jazeera SMS service has been compromised by hackers who have sent fake news," the TV channel said in a tweet.
Another fake text message suggested the wife of Qatar's emir, Sheikha Moza bint Nasser Al Missned, had been wounded.
It is the fourth such incident since the conflict in Syria intensified. Last week, al-Jazeera Arabic's website was defaced, with a Syrian flag posted on the front page.
That time, a group calling itself al-Rashedon claimed responsibility.
In February, the SEA said it had been behind an attack on al-Jazeera English's website, and in July the same group gained access to the organisation's Twitter account and began posting stories denouncing the Syrian opposition fighters.
Qatar has been supportive of the Syrian rebels fighting against President Bashar al-Assad's regime, and al-Jazeera has covered the Syrian conflict extensively since it began.
The SEA has also targeted Saudi-owned Al Arabiya News and the Harvard University website.
A Twitter account run by the Reuters news website was also hacked by Syrian government supporters in August.