The plane went down 239 km from the greek island of Karpathos.
Here is the last location of the plane:
FlightAware.com still shows position information recorded after the last known location of the plane. I have no idea what that data actually indicates though.
http://flightaware.com/live/flight/MSR804/history/20160518/2045ZZ/LFPG/HECA
Right in the middle of the Mediterranean! Just inside their airspace.