Berlin: The captain locked out of the cockpit of the Germanwings plane that crashed in the French Alps used an axe to try and force his way back in, German daily Bild said on Friday, citing security sources.

Co-pilot Andreas Lubitz appeared to have deliberately flown the plane into the side of a remote mountain after locking the captain out of the cockpit, French officials have said, killing himself and all 149 others aboard on Tuesday.

The cockpit flight recorder showed that the captain repeatedly knocked and tried to get back in as the plane went into its fatal descent, French prosecutors said. However, Bild reported that the captain also tried using an axe to break down the cockpit`s armoured door.

This could not be immediately confirmed, but a spokesman for Germanwings confirmed to a news agency that an axe was on board the aircraft.

Such a tool is "part of the safety equipment of an A320," the spokesman told Bild.