French anti-terror prosecutors have launched an investigation into a cyber attack, which took state-owned TV5 Monde off air late Wednesday and into the following day.
A total 11 channels were simultaneously blacked out by hackers claiming allegiance to the "Islamic State" (IS) group.
They also took over the website and social media accounts belonging to the French global television network.
TV5 Monde boss Yves Bigot said it was a cyber attack "unprecedented in the history of television."
"Their goal was maybe to broadcast their message on our airwaves and not only social networks and our website," he added. "They may have wanted... to take our airwaves hostage."
Attack "linked to terrorism"
The channel resumed full operations on Thursday, 18 hours after the "unprecedented" cyber attack began.
French Culture Minister Fleur Pellerin warned other media outlets to be vigilant, saying another attack could not be excluded and may even be in the planning stages.
Interior Minister Bernard Cazeneuve said the incident was probably linked to terrorism.
"Numerous elements converge to suggest the cause of this attack is, indeed, a terrorist act," he said at a news conference.
Cazeneuve also said France was "absolutely determined to catch those who want to strike at its heart."
The TV5 Monde website was infiltrated by a group calling itself "Cybercaliphate," which posted the message, "I am IS" in French.
The group has carried out attacks against other media outlets - including several in the US - since late last year.
The IS group had targeted France in the past for joining an international coalition set up to fight Islamic extremists.
The power to black out a global television network represented a new level of sophistication for the group, French officials said.
The country is still reeling from deadly shootings in Paris in January at the satirical magazine Charlie Hebdo and a Jewish grocery store.
TV5 Monde was founded by the government in 1984 and describes itself as the "worldwide French cultural channel."
lw/rc (AP, AFP, Reuters)