Cairo: An EgyptAir plane en route from Paris to Cairo carrying 66 people crashed in the Mediterranean Sea today after plunging 22,000 feet and swerving sharply with Egypt saying the possibility of a terror attack or a technical error could not be ruled out.

"I will use the words 'the missing plane' until we find the debris or be certain about what happened,"Egypt's Civil Aviation Minister Sherif Fathi said in a press conference.

"We don't deny the possibility of a terror attack or a technical error," he said.

EgyptAir Flight 804 from Paris to Cairo disappeared from radar with 66 people on board, the airline said.

French President Francois Hollande confirmed that the EgyptAir Airbus A320 had "crashed".

"We must ensure that we know everything on the causes of what happened. No hypothesis is ruled out or favoured," he said in a televised address.

"Whether it was an accident or another hypothesis that everyone has on their mind -- a terrorist hypothesis... At this stage we must focus on our solidarity with the families and the search for the causes of the catastrophe," Hollande said.

Paris prosecutor's office said its accident department had opened an investigation into the incident.

Greece's Defence Minister Panos Kammenos said the plane fell 22,000 feet and swerved sharply in Egyptian airspace before it disappeared from radar screens.

"The plane carried out a 90-degree turn to the left and a 360-degree turn to the right, falling from 37,000 to 15,000 feet and the signal was lost at around 10,000 feet," Kammenos told a newsconference.

"It appears the plane is lost. There are no clear results (from the search) so far," he said.

However, Greek Aviation officials said earlier that air traffic controllers had spoken to the pilot a few minutes earlier and everything had appeared normal.

The plane was carrying 56 passengers -- including three children -- seven crew members and three security personnel.

Apart from 30 Egyptians, the plane was carrying 15 French passengers, two Iraqis and one each from Britain, Belgium, Kuwait, Saudi Arabia, Sudan, Chad, Portugal, Algeria and Canada.

Egypt and Greece both had both dispatched aircraft and naval vessels on a search mission and they were expected to be joined by French teams.

The plane is believed to have been lost some 130 nautical miles from the island of Karpathos, between Crete and Rhodes.

The plane lost contact with radar after it entered Egyptian airspace, around 280 kilometres off the country's coastline north of the Mediterranean port city of Alexandria.

The aviation officials later said the plane crashed and that a search for debris was now underway.