Several staff members have been injured when the nose gear of a Boeing 787 jetliner unexpectedly collapsed at a gate at Frankfurt airport, its operator Lufthansa says.

"Passengers had not yet boarded," a company spokesperson said in an emailed statement, adding that crew members and ground staff were on board the aircraft at the time of the incident.

Lufthansa said 13 crew members were on board, along with an unspecified number of airline and contractor employees preparing the Boeing 787-9 Dreamliner before passenger boarding.

Two Lufthansa cabin crew employees and other staff from service providers were taken to hospital, a company spokesman said.

He did not provide details on the severity of the injuries or the total number of people hurt.

A Reuters photographer saw multiple emergency vehicles parked around the two-engine wide-body aircraft, which partly lay on its belly.

A video shared by tracking website Flightradar 24 shows the nose gear of the aircraft snapping, causing the body of the plane to crash to the ground.

An airport worker warning a safety vest can be seen close to the plane's nose as the aircraft collapses, jumping back to avoid being hit.

Another worker can be seen standing on top of a cargo lift on the right-hand side of the aircraft.

Both appeared to be unharmed.

The incident occurred at 12.45pm and the jet was scheduled to depart for Los Angeles as flight LH450, Lufthansa said.

Once cleared by authorities, the aircraft is expected to be moved to a maintenance hangar for further examination before repairs begin.

"We are currently investigating the exact circumstances with the relevant authorities," the company added.

The 787, of which Lufthansa operates the 787-9 variant, is a relatively new addition for the group, which is planning to gradually phase out less efficient jets and simplify its fleet.

with DPA