About 45 people were injured when a Northwest Airlines flight from Manila to Tokyo's Narita airport hit severe turbulence on Friday.

Northwest said 45 people were taken to a local hospital for medical treatment and five people remain in hospital. There were no fatal injuries.

The Boeing 747-400 carrying 408 passengers and 14 crew, was on approach to Narita when it hit the turbulence.

Northwest Airlines last year merged with Delta Air Lines.