French TV station back on air after being hacked by ISIL supporters

France's TV5Monde television channel has resumed full operations after an "unprecedented" hack by self-proclaimed Islamic State militants, who shut down transmissions and hijacked its website and social networks.

Authorities said the hack was likely a "terrorist act" and urged media companies to be "vigilant", warning that further attacks could not be ruled out.

Interior Minister Bernard Cazeneuve said: "There are a lot of elements that suggest that a terrorist act" was to blame for the shutdown at the Paris-based station, whose programs are broadcast in more than 200 countries worldwide.

For most of Thursday, the channel was forced to broadcast pre-recorded programs after what TV5Monde boss Yves Bigot said was a cyber-attack "unprecedented in the history of television".

The hackers took control of the station and its social media operations late on Wednesday.

By seizing the IT system, they were able to black out the TV channels for several hours.

The self-styled cyber jihadists also posted documents on its Facebook page purporting to be the identity cards and CVs of relatives of French soldiers involved in anti-IS operations, along with threats against the troops.

"Soldiers of France, stay away from the Islamic State! You have the chance to save your families, take advantage of it," read one message on TV5Monde's Facebook page.

"The CyberCaliphate continues its cyberjihad against the enemies of Islamic State," the message added.

The defence ministry in Paris said it was working to verify whether the documents were genuine.

"Everything is being done to find those who carried this out, punish them, re-establish the programs and prevent cyber terrorists threatening freedom of expression in the future," Foreign Minister Laurent Fabius also said.

The hackers had accused French President Francois Hollande of committing "an unforgivable mistake" by getting involved in "a war that serves no purpose".

"That's why the French received the gifts of Charlie Hebdo and Hyper Cacher in January," it said on the broadcaster's Facebook page, referring to attacks by Islamist gunmen in Paris on the satirical magazine and Jewish supermarket that left 17 people dead.

France is part of a US-led military coalition carrying out air strikes against IS in Iraq and Syria, where the jihadist group has seized swathes of territory and declared an Islamic "caliphate".