China's Air Force sent more than 40 aircraft to the West Pacific near the Japanese island of Okinawa on Sunday, for what state-media called routine drills.

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China says fleet of military aircraft were carrying out routine drill

Japan says Chinese military activities have been expanding

Tokyo CNN  — 

Japan scrambled fighter jets Sunday after China flew a fleet of aircraft near contested islands in the East China Sea.

Japanese Chief Cabinet Secretary Yoshihide Suga said that the jets were sent up after eight Chinese military planes crossed between Okinawa and the Miyako islands near Taiwan. He said that two of the aircraft were thought to be fighter jets.

He added that the planes didn’t “trespass” into Japan’s territorial airspace, although he said it was the first time that Chinese military aircraft had been seen in the Miyako Strait.

The fleet included H-6k bombers, Su-30 fighters and air tankers.

“We will continue to keep close eyes on the Chinese military activities which have been expanding and become more frequent,” he said.

Shen Jinke, an official with the People’s Liberation Army Air Force, said that a fleet of 40 aircraft were sent to the West Pacific via the Miyako Strait Sunday for a “routine drill on the high seas,” according to China’s official Xinhua news agency.

The fleet, which included H-6K bombers, Su-30 fighters and air tankers, simulated reconnaissance and early warning attacks on sea-surface targets. It also conducted in-flight refueling to test the Air Force’s fighting capacity, Xinhua added.

Japan scrambled a fighter jet as 8 Chinese planes flew over the Miyako Strait.

The report added that the fleet conducted routine patrols in China’s Air Defense Identification Zone (ADIZ), which the country set up in the East China Sea in 2013 despite objections from Tokyo and Washington.

Japan rejects the ADIZ, which encompasses disputed islands that are known as the Senkakus in Japan and Diaoyu in China.

Japan also has an ADIZ over the islands, which it administers.

Shen said the drills and patrols were conducted “in accordance with the needs of the Air Force to defend national sovereignty and security, as well as to maintain peaceful development.”

Both China and Japan claim ownership of the islands and tensions have flared numerous times in recent years.

While they are uninhabited, their ownership would allow for exclusive oil, mineral and fishing rights in the surrounding waters.

In mid-2014, Japanese and Chinese jets had a tense standoff in a region where both zones overlap, with Japan’s Defense Minister saying the planes at one point came within 30 feet of each other.

Tensions have flared in the region in recent years.

Tension over the island dispute has in the past spilled over into protests and violence against Japanese-owned businesses in China.

The Senkaku/Diaoyu islands are by no means the only islands whose ownership China disputes.

READ: South China Sea: China may establish ADIZ

Beijing claims the majority of the South China Sea as part of its territory, which has led to heightened tensions and frequent disputes with its neighbors there.