Amazon Japan’s store shelf-carrying robots save time for staff to move around between shelves at a high-tech Amazon Japan warehouse in Ibaraki, Osaka Prefecture, on April 4. (Satoru Ogawa)

IBARAKI, Osaka Prefecture--An army of Amazon Japan robot discs briskly hauled tall shelves stacked with items across the firm's warehouse floor here on April 4.

The online retail giant installed the orange robots to accelerate efficiency in receiving items arriving at its warehouse and shipping them out to customers.

Touting its high-tech distribution Amazon robotics system, which began full-scale operations in April, the Japanese arm of U.S.-based Inc. opened its cutting-edge distribution base to media representatives on the day.

It is the firm's second such facility in Japan following one it operates in Kawasaki, Kanagawa Prefecture.

The slim robots, which resemble Roomba robot vacuums, glide automatically through the warehouse on wheels at a speed of 1.7 meters per second. They were upgraded to carry items of up to about 567 kilograms, over 200 kg more than those in the Kawasaki warehouse, a move the firm says paid off in increased efficiency.

People working with the robots don't need to memorize the whereabouts of items since the robotics system also manages the warehouse shelves.

Staff stay in a designated spot and follow instructions on a monitor, retrieving items from the shelves the robots bring over, and stowing them in containers to be shipped.

In contrast to traditional warehouse operations, no specific shelves are allocated to particular items. The system links items and available shelves as they arise.

The space the shelf-carrying robots move around in is off-limits for humans and partitioned off by a fence, which ensures safety, the company said.