Seven crew members are reportedly missing and one injured after a US Navy destroyer collided with a merchant ship off the coast of Japan.

The USS Fitzgerald was damaged below the water line on its starboard side and there was flooding in three compartments, the navy confirmed.

Footage from Japanese TV network NHK showed a crew member being airlifted on a stretcher to a helicopter.

Another navy vessel, the USS Dewey, medical assistance and two navy tugs were said to have been sent to the scene. Naval aircraft were also being readied.

The US 7th Fleet said on its Facebook page that it was working with the Japanese Coast Guard to conduct a medical evacuation for a sailor who reportedly to have had a head injury.

Details of his or her condition were unknown.

The coastguard said it received an emergency call from Philippine-registered container ship ACX Crystal at around 2.20am local time on Saturday. (6.20om Friday BST) that it had collided with the Fitzgerald south west of Yokusuka, Japan.

The Fitzgerald collided with the merchant ship 56 nautical miles from Yokosuka, a city south of Tokyo that is home to a major US naval base.

Rita Schrimsher from Alabama whose grandson, Jackson Schrimsher, 23, is a sailor onboard, said: "Of course we're nervous and scared and just praying."