°®Âþµº

Militants could imminently launch a "terrorist campaign" of bombings in public places, DGSI agency Chief Patrick Calvar said at a meeting on national defence last week, adding France was "the country most threatened" by IS as well as Al-Qaeda.

"We know that Daesh [the Arabic acronym for IS] is planning new attacks - using fighters in the area, taking routes which facilitate access to our territory - and that France is clearly targeted," Calvar said.

"We risk being confronted with a new form of attack: a terrorist campaign characterised by leaving explosive devices in places where big crowds gather, multiplying this type of action to create a climate of panic," he said.

Preparations are at an advanced stage for the Euro 2016 international football tournament due to launch in Paris next month.

Just hours after the comments were made public, reports emerged suggesting the crash of flight MS804 could have been a "terror attack".

Aviation experts said theories suggesting mechanical malfunction in the case of this particular crash were unlikely.

"A major technical fault - the explosion of a motor, for instance - seems improbable," said aeronautics expert Gerard Feldzer, saying the A320 aircraft in question was "relatively new".

"It's a modern plane, the incident happened in mid-flight in extremely stable conditions. The quality of the maintenance and the quality of the plane are not in question in this incident," Jean-Paul Troadec, former director of France's aviation Bureau of Investigation and Analysis, told Europe 1 radio.

Greek civil aviation said no problem was mentioned when the pilot sent the last signal 25 minutes before the plane disappeared near Athens.

"A technical problem, a fire or a motor malfunction, doesn't cause an instantaneous accident and the crew has time to react," said Troadec.

"Here, the crew didn't say anything."

Twenty-six foreigners, including 15 French citizens, two Iraqis, a Briton and a Canadian, were believed to have been among the 56 passengers on board the flight, EgyptAir said.

The Islamic State group has been waging a deadly insurgency against Egyptian security forces, and last October claimed the bombing of a Russian airliner flying holiday-makers home from the Egyptian resort of Sharm al-Sheikh. All 224 people on board were killed.