The USS Bonhomme Richard was in port in San Diego for maintenance when the explosion and fire broke out around 9:00 am, according to the Navy Times.

Scenes broadcast by CNN showed thick smoke billowing from large sections of the ship, as fireboats used water cannon to try to control the blaze.

The official Twitter account of Naval Surface Forces, US Pacific Fleet, said 11 sailors were taken to hospital for minor injuries. Several firefighters reportedly also suffered burns and smoke inhalation.

Colin Stowell, head of the San Diego fire department, told CNN that the fire could go on "for days" and "just burn down to the waterline."

The cause of the explosion was not immediately clear.

The Navy Times quoted a navy spokeswoman as saying about 200 sailors and officers were on board at the time. San Diego is the ship's home port.