A total of 24 Russian warships have been operating in the Sea of Japan and the southern part of the Sea of Okhotsk since Feb. 1, the Defense Ministry said Tuesday, in what defense chief Nobuo Kishi called part of “unusual” large-scale military exercises.

"The move comes in concert with Russian forces' recent activities in areas near Ukraine," Kishi told a news conference Tuesday, noting that Russia's military was believed to be stepping up its activities to highlight that it remains capable of operating both on the east and west of the country at the same time.

Russia has more than 100,000 troops massed near Ukraine, stoking fears of an impending invasion.