Japan's Defense Ministry says four Russian and Chinese military vessels have been confirmed to have passed through a strait in southwestern Japan.

The ministry says the Maritime Self-Defense Force identified two Russian navy ships including a frigate and two Chinese navy ships including a missile destroyer.

The ships were confirmed to have cruised eastward about 40 kilometers off the Kusagaki Islands in Kagoshima Prefecture on Thursday afternoon.

Officials say the vessels passed through the Osumi Strait in southwestern Japan later on Thursday and Friday, and traveled toward the Pacific Ocean.

It is the third time that Russian and Chinese naval vessels were observed passing through the strait together. The previous observation took place in September 2022.

Russia's defense ministry announced on Thursday that vessels from the two countries would conduct joint patrols. Japan's Defense Ministry is closely monitoring their activities.