COLOGNE, Germany (AFP) - Lufthansa chief executive Carsten Spohr said on Thursday he was "stunned" by suggestions the co-pilot of the jet operated by its Germanwings subsidiary had deliberately crashed the plane.

Mr Spohr told a news conference there was "no indication what might have led" to the actions of Andreas Lubitz.

He added that no security "system in the world" could have prevented the co-pilot's actions.

He also said that the 28-year-old Lubitz had passed all psychological tests required to begin training and underwent regular physical examinations.

Germany's Interior Minister Thomas de Maiziere told reporters that based on the information known so far about Lubitz there was no indication of "a terrorist background", echoing comments by French officials.

Lubitz, had worked for Germanwings, a Lufthansa subisidiary, since September 2013, a Lufthansa spokesman said on Thursday.

He qualified as a pilot at the Lufthansa training centre in the northern city of Bremen and began flying for Germanwings immediately after completing the course. He had 630 hours of flight experience, she said.

Lubitz was from the western town of Montabaur and lived with his parents there while keeping a flat in Duesseldorf, a Germanwings hub and the city for which the doomed flight from Barcelona was bound, Montabaur mayor Gabriele Wieland told national news agency, DPA.

The captain of the two-man crew, who has not been identified, had more than 10 years of experience with German flag carrier Lufthansa and its subsidiaries and had clocked up more than 6,000 hours of flight time, most of them on Airbus planes.

The daily Bild named him only as German national Patrick S., in keeping with strict privacy laws, and said he was a father of two children.

Lufthansa said it had no plans to name the flight personnel at this stage of the investigation "to protect the crew and their families", a spokesman told AFP.