MANILA - China has deployed a military aircraft to a base it built on a reclaimed island in the South China Sea, photos from an American think tank released Wednesday confirmed.

The Asia Maritime Transparency Initiative published photos taken from April 28 showing a military aircraft, a Shaanxi Y-8, at Subi Reef in the Spratly Islands.

AMTI said the Y-8 was "designed as a military transport aircraft, but some variants are used for maritime patrol or signals intelligence."

"This should be particularly concerning to the Philippines, which has about 100 civilians and a small military garrison on Thitu Island just 12 nautical miles away," the think tank said.

It added, with the recent deployment, military aircraft have landed on all three of China’s airstrips in the Spratly Islands after a naval patrol aircraft also landed at Fiery Cross Reef in April 2016 and 2 Xian Y-7 military transport aircraft were seen on Mischief Reef in a photo dated January 6.

The Permanent Court of Arbitration has ruled in 2016 that Mischief Reef is part of the Philippine continental shelf.

Apart from the aircraft, military jamming equipment were also sighted in Mischief and Fiery Cross reefs. AMTI said the systems were visible in satellite imagery of Mischief from at least mid-February, and were still present as of May 6, although placed under covers.

American television network CNBC, citing sources close to United States intelligence, earlier reported that the Chinese army installed anti-ship and air-to-air defenses on outposts in Fiery Cross Reef, Subi Reef and Mischief Reef.

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AMTI noted that China's deployments in the 3 reefs followed a "pattern" it also set at Woody Island in the Paracel Islands, where it has rival claims with Vietnam and Taiwan.

"From harbor dredging and runway improvements to hangar and radar construction, upgrades at Woody Island have served as a blueprint for things to come on China’s Spratly holdings to the south," the think tank said.

Beijing deployed HQ-9s and anti-ship cruise missiles (YJ-62s) to Woody in 2016. Satellite imagery also captured five Y-8 aircraft on the island in November 2017, said AMTI.

"Considering that China has built identical hangars for combat aircraft at Woody and on each of the Big Three, it is likely that J-10s or J-11s will soon find their way south to the Spratly Islands," it said, pertaining to 2 kinds of fighter jets.

Satellite images from AMTI also showed that China's destroyers, frigates, combat ships and patrol vessels "regularly visit the artificial islands, along with many auxiliary and logistics vessels," underlying the presence of the People’s Liberation Army Navy and China Coast Guard in the area.

Apart from combatant and law enforcement vessels, AMTI said an array of support ships, including tankers, tugboats, and replenishment vessels, as well as an oceanographic surveillance ship have been seen.

Presidential Spokesperson Harry Roque said "any possible scenario that would encourage military action in our backyard, in our exclusive economic zone" would be "troublesome."

However, he said the Philippines is also confident it is not the target of the missiles because of the friendship between China and the Philippines.

“We are exploring all diplomatic options which does not mean we are not doing anything,” he told reporters at a briefing in Malacañang.

“I was, from the very beginning, saying we are concerned. But you can’t ignore the fact that because of our very good relations, we are confident China as a country does not view us as a threat.”

The arbitration court in 2016 rejected Beijing's historic claims to most of the South China Sea, acting on the case brought by former President Benigno Aquino III after a standoff between Chinese coast guard ships and a Philippine naval vessel in the Scarborough Shoal.

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While it clarified the status of territories within the disputed waters, it did not rule on the matter of sovereignty or ownership.

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President Rodrigo Duterte set this decision aside as he distanced Manila from its traditional ally, the United States, and embraced China, seeking financial and military aid.

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