Egyptian authorities found luggage, a seat and a body part during the search for an EgyptAir jet which plunged into the Mediterranean, Greece's defence minister said on Friday.

"A short while ago we were briefed by the Egyptian authorities ... on the discovery of a body part, a seat and baggage just south of where the aircraft signal was lost," Defence Minister Panos Kammenos told reporters in Athens.

The flight with 66 people on board vanished minutes after leaving Greek for Egyptian airspace on Thursday morning.

Kammenos said Greece could not speculate on the reasons the aircraft crashed. He reiterated that Greek radars picked up sharp swings in its trajectory as it plunged from a cruising altitude to 15,000 feet, then vanishing from radars.