France may have frozen the delivery of the controversial "Mistral-class" helicopter gunship to Russia, but its construction is still ongoing, a well-informed source said on Thursday.

Fifty-five Greenpeace activists from some 20 countries go on trial in France on Thursday for an audacious break-in at the country's oldest nuclear power plant to highlight weaknesses at atomic installations. 

French President Francois Hollande on Wednesday raised the prospect of a military response to the threat posed by Islamic State extremists occupying swathes of Iraq and Syria, saying it may be necessary.

"The head of state underlined the importance of a political, humanitarian and if necessary military response in accordance with international law" to fight against IS, the presidency said in a statement summing up a restricted defense meeting.

France said Wednesday "conditions" were not in place to deliver the first of two Mistral-class warships to Russia, a move planned later this year that has sparked controversy given the crisis in Ukraine.

"The President of the Republic declared that, despite the prospect of a ceasefire which still remains to be confirmed and implemented, the conditions for France to deliver the first warship are not to date in place," Francois Hollande's office said in a statement, on the eve of a major NATO summit.

France's prime minister will hold a parliamentary vote of confidence on September 16, the presidency said Wednesday, as the ruling Socialist party suffers a crisis that mirrors that of the entire country.

Manuel Valls had already announced his intention to hold the vote last week, shortly after tendering the government's resignation when his firebrand, left-wing economy minister publicly challenged the country's economic direction. Valls replaced him with a former banker in the quick reshuffle that ensued.

A far-right weekly has sparked a firestorm of controversy by describing France's new education minister as a "Moroccan Muslim" and calling the appointment of the 36-year-old rising star a "provocation".

Morocco-born Najat Vallaud-Belkacem is the first woman in French history to hold the office of education minister, the latest step in a brilliant career for the telegenic protegee of President Francois Hollande.

A young French mother whose daughter had been smuggled out of the country by her father arrived home with the two-year-old girl on Wednesday after they were reunited earlier in Turkey.

Two Frenchmen allegedly involved in the hit-and-run death of an Israeli woman in Tel Aviv will stand trial in Paris on November 27, judicial sources told Agence France-Presse Tuesday.

Lee Zeitouni, 25, was hit by a speeding car on a city street in September 2011 and left to die when the car failed to stop.

France's scorned former first lady Valerie Trierweiler is set to lift the lid on her relationship with the president this week in what could prove an explosive memoir, media reports said Tuesday.

Trierweiler, a 49-year-old journalist, was dumped unceremoniously by Francois Hollande in January after a magazine revealed his affair with actress Julie Gayet, and has since remained broadly silent about an event she once said had felt like falling "from a skyscraper."

A French Islamist suspected of heading a militant network told a Belgium court Tuesday that he took part in a deadly ambush against African peacekeeping troops in Somalia.

The retrial of Frenchman Rachid Benomari opened at a time of mounting concern over the number of Europeans believed to be traveling to Syria, Africa and the Afghan-Pakistani border to fight alongside jihadist groups.