Germany has lifted a flight ban on the fleet of Airbus Helicopters Tiger attack rotorcraft operated by its army, but has yet to restart operations with the type.

Berlin grounded the Tiger, except for operational emergencies, following a late-July fatal crash near Gao in Mali in which two servicemen were killed.

Although the investigation into the accident has yet to reach any conclusions, the German defence ministry believes the helicopter is safe to fly again, with certain restrictions in place.

These relate mainly to speed and weight limits, as well as use of the autopilot. It says the constraints on the helicopter's use are "low and acceptable".

"[The inquiry] has cleared a lot of factors," it says. "It is clear to fly again under certain circumstances but we do not know yet the exact reason for the accident."

It says a series of tests will be performed on its 51-strong Tiger fleet, prior to the restart of operational flights.

Little detail has emerged from the crash investigation, but the Tiger appears to have lost its main rotor blades after entering into a sudden steep descent.

It hit the ground around 10s later, and the wreckage was consumed by a post-impact fire.

The defence ministry says the inquiry is looking at the ill-fated Tiger's flight control system as a potential cause of the accident, as its operation appears to have differed from that recorded on similar aircraft.