The U.S. Naval Hospital Ship Mercy in port. (Video footage by Takahiro Kumakura

A converted oil tanker that now ranks as one of the world's largest floating hospitals made its first stop in Tokyo late June 15.

The U.S. Naval Hospital Ship Mercy, which docked at Oi Marine Products Wharf in Tokyo's Ota Ward, is equipped with about 1,000 beds, 12 operating theaters, an intensive care unit and CT scanning equipment.

Its main mission is to provide medical care for combat troops wounded in action. It was deployed to the Persian Gulf in 1990 before the start of military combat in Iraq.

It can transport a maximum of 1,300 people, including medical personnel.

The Japanese government invited the Mercy to Japan to gain a better understanding of ways to provide emergency medical care during natural disasters.

The Mercy measures 272 meters stern to bow and has a displacement of 69,360 tons when carrying a full load.

Refitted from an oil tanker and handed over to the U.S. Navy as a hospital ship in 1986, it was involved in a joint training exercise with the Maritime Self-Defense Force on June 14 at Yokosuka Naval Base in Kanagawa Prefecture.

The drill was to simulate loading a large number of casualties onto the ship to undergo emergency medical treatment after a natural disaster.

Local residents chosen by lottery were to get a rare view of the ship on June 16.