TOKYO (Kyodo) -- Japan confirmed for the first time two Chinese aircraft carriers operating simultaneously in the Pacific, as the government said Monday it has spotted the Shandong near Japan's southernmost Okinotori island, a move further fueling Tokyo's concerns over Beijing's military activities.

The announcement came a day after the Defense Ministry said the Chinese aircraft carrier Liaoning was observed in the vicinity of Japan's easternmost Minamitori Island in the Pacific for two days from Saturday, the first confirmed navigation by a Chinese carrier in those waters.

Together with four vessels including a missile destroyer, the Shandong was sailing through waters 550 kilometers southeast of Miyako Island in the southern prefecture of Okinawa on Saturday around 1 p.m., according to the ministry.

On Monday, the Shandong, commissioned in 2019 as China's second aircraft carrier, conducted landing and takeoff drills involving its fighter jets and helicopters north of the Okinotori, some 1,700 km south of Tokyo, within Japan's exclusive economic zone, the ministry said.

Meanwhile, the Liaoning, along with two destroyers and another vessel, was seen in waters about 300 km southwest of Minamitori, which is approximately 1,900 km southeast of Tokyo, at around 6 p.m. Saturday, according to the ministry. The area lies within Japan's EEZ.

The Liaoning then moved southwest and conducted landing and takeoff drills with its fighter jets and helicopters on Sunday outside the EEZ.

The Liaoning was observed beyond what is known as the "second island chain" stretching from Japan's Izu Islands to Guam, a Japanese government official said. China considers the chain its defense line.

Following the Liaoning's move, Chief Cabinet Secretary Yoshimasa Hayashi said earlier Monday that Japan will continue to closely monitor China's growing maritime activity and step up surveillance, saying that China apparently intends to "enhance its capability to carry out missions at sea and in the skies farther away" from its shores.

"We will do our utmost to perform our warning and surveillance duties at sea and in the air," Hayashi, the top government spokesman, told a regular press conference, adding Japan has conveyed its position to China regarding the latest development.

Chinese Foreign Ministry spokesman Lin Jian defended the aircraft carrier's activities, saying at a press conference Monday that they are "fully consistent with international law and international practices."

Lin said China pursues a national policy that is "defensive in nature," expressing hope that Japan will view its activities "objectively and rationally."

Commissioned in 2012 as China's first aircraft carrier, the Liaoning is a refurbished Soviet-made vessel purchased from Ukraine in the late 1990s and features a "ski-jump" takeoff ramp.