Japan began releasing treated wastewater from the stricken Fukushima-Daiichi nuclear power plant into the Pacific in August, 12 years after it suffered one of the world's worst atomic accidents.

Tokyo insists that the water being released is harmless and is heavily diluted with seawater, a view backed by the International Atomic Energy Agency, but China and Russia have criticised the release and banned Japanese seafood imports.

"The sale of Japanese seafood at US base commissaries will help confront China's arbitrary and unjust embargo on Japan's seafood exports," US ambassador Rahm Emanuel said in a statement.

The commissary store at the Yokota US Airbase received on Tuesday the first shipment of scallops from the northern Japanese island of Hokkaido after an initial order of 800-900 kilos.

US bases "will procure additional seafood products in the coming weeks and months," the embassy said.

It will also be served in base messes and onboard US naval vessels deployed to Japan, it added.

Japan is home to 110,000 US service members and their families, the statement added.

Operator TEPCO completed releasing the second batch of wastewater from the plant in late October, with a third round to be released starting Thursday.