Japan's Defense Ministry says a group of Chinese naval vessels, including an aircraft carrier, sailed from the Pacific Ocean to the East China Sea through waters between two islands of Okinawa Prefecture on Saturday.

Ministry officials assume the vessels conducted training in the Pacific.

They say the carrier Liaoning, accompanied by six other vessels, passed between Okinawa's main island and Miyakojima island in southwestern Japan.

The Liaoning had navigated through the same waterway in the opposite direction on May 2.

The ministry says fighter jets and helicopters were seen taking off from and landing on the Liaoning more than 300 times in the Pacific on and after May 3.

Officials believe the training was part of the Chinese navy's efforts to enhance its capability to execute operations in distant waters.

The ministry is continuing monitoring and conducting a detailed analysis of the carrier's moves.

This is the fourth time the carrier was seen sailing round-trip through the waters between the islands.