A US Navy destroyer collided with a Philippine-flagged container ship off the coast of Japan early Saturday, leaving seven crew members from the American vessel unaccounted for, the Japanese Coast Guard said.
The collision between the guided missile destroyer USS Fitzgerald and the ACX Crystal took place south-west of Yokosuka, Japan at about 2:30 am Saturday (1730 GMT Friday), the US Navy and Japan's coastguard said.
The Navy also said the Japanese were helping to evacuate one sailor by helicopter, indicating injuries serious enough to rush the person back to shore for treatment.
The coastguard said it was looking for the seven missing crew based on information it had received from the US Navy.
"We are currently searching for the missing individuals," a coastguard spokesman said, also confirming that another crew member had sustained serious injuries.
In a statement released earlier on Twitter, US chief of naval operations Admiral John Richardson said: "As more information is learnt we will be sure to share it with the Fitzgerald families.
"All of our thoughts and concerns are with the Fitzgerald crew and their families."
The Japanese coastguard has sent five vessels, two planes and a team of specially trained rescue personnel to the area, the spokesman said.
Video taken by Japan's public broadcaster NHK showed heavy damage to the starboard side of the Fitzgerald just ahead of the control tower, and that the ship had taken on water.
The footage meanwhile showed relatively light damage on the port bow of the ACX Crystal.
"The USS Fitzgerald suffered damage on her starboard side above and below the waterline. The collision resulted in some flooding," the Navy said.
The Navy said the Fitzgerald was still under its own power "although her propulsion was limited."
A US defence official told AFP that "sailors are de-watering" flooded areas of the ship.
The 154-metre (505-foot) Fitzgerald is based at Yokosuka, south of Yokohama and Tokyo, and operates in the Pacific and the Sea of Japan.
The ACX Crystal is a 222-metre commercial container ship that, according to marine tracking websites, was on its way to Tokyo.
The ship carries a Philippine flag but is listed as owned by Japanese shipping giant NYK Line.