Shafaq news/ An explosion on a United States Navy ship moored at a base in California set off a major fire on Sunday injuring 21 people - 17 of them sailors, according to the chief of naval operations.

The USS Bonhomme Richard, an amphibious assault vessel, was in port at its home base in San Diego for maintenance when the explosion took place at about 8.30am local time on Sunday (15:30 GMT).

"We are grateful for the quick and immediate response of local, base, and shipboard firefighters aboard BHR," the naval-operations chief wrote on Twitter, referring to the Bonhomme Richard. "Our thoughts and prayers are with our BHR Sailors, their families, and our emergency responders who continue to fight the fire."

Thick smoke could be seen billowing from large sections of the 844-foot (257-metre) warship, as firefighters on tugboats tried to control the blaze using water cannon.