The Philippine government on Thursday released military surveillance photos of Chinese land reclamation on a reef claimed by Manila in the South China Sea that it said showed Beijing violated a regional agreement not to escalate territorial disputes.

Foreign Affairs Department spokesman Charles Jose said the pictures show Chinese aggressiveness in asserting its claims over the entire South China Sea.

The aerial photographs were accompanied by a caption stating that they were obtained from "Philippine intelligence sources." The caption said the "extensive reclamation" by China on the Johnson South Reef, called Mabini by Manila and Chigua by Beijing, was "destabilizing."

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The Chinese Embassy in Manila had no immediate comment, but a Foreign Ministry spokesman in Beijing has said that the area is part of China's territory, and that any Chinese activities at the reef should be of no concern to Manila.

Jose noted that a 2002 nonbinding agreement between China and the 10-member Association of Southeast Asian Nations calls for restraint in conducting activities in the region that would "complicate or escalate disputes" and to not inhabit uninhabited areas

"We want to show people that (China's) actions are part of its aggressive behavior to assert its claim in violation of the DOC," or Declaration on the Conduct of Parties in the South China Sea, which was signed by China, Philippines and nine other ASEAN members, Jose said.

Philippine President Benigno Aquino III said a stronger accord and international arbitration would offer more lasting solutions to the territorial conflicts. A proposed legally binding "code of conduct" between China and Southeast Asian countries is seen as a mechanism to prevent a major armed conflict in the disputed waters. Manila sought international arbitration against Beijing in January 2013 after Chinese government ships took control of a shoal claimed by the Philippines off its main island of Luzon.

Philippine Foreign Secretary Albert del Rosario said Wednesday that it was not clear what China would build on the reclaimed land, but that an airstrip was a possibility.

A senior government official, speaking on condition of anonymity because he was not authorized to talk about the issue, said it could also be used as a military base and a resupply and refueling hub. The official said the reclamation was first detected by air force planes six months ago.

Defense Secretary Voltaire Gazmin said the Philippine military has been monitoring Chinese activities at the reef for several months. "For whatever purpose (the reclamation was done) we still do not know, but we are almost sure that there will be a base," he told reporters Thursday.

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An airstrip or a military base on the reef would boost the mobility of Beijing's naval and air forces in the South China Sea region, far from the Chinese mainland.

The pictures showed "before-and-after" images — from an untouched reef in 2012, followed by another showing a concrete building jutting out of the water, and the reclaimed land two years later. Philippine aircraft helping search for the missing Malaysian Airlines plane in March reported reclamation work was continuing, Jose said.

Del Rosario said Manila lodged a protest against China last month, but that Beijing has ignored it.

Chinese Foreign Ministry spokeswoman Hua Chunying said in Beijing on Wednesday that the reef was part of China's territory and any construction there is covered by its "sovereignty rights."

The Philippine government estimates that the Chinese have reclaimed a land mass of at least 30 hectares (74 acres) from the reef, which Manila says is part of its western Palawan province. What has emerged from the coral outcrop appears like a vast tree-less island of white sand in the middle of turquoise blue waters.

One of the released pictures shows a long pipe connected to a large dredging vessel on the northwestern edge of the reef. A concrete building, likely to be China's outpost on the reef, stands on the southern edge of the emerging islet. A ship is anchored close by.

The reef, part of the Spratly Islands chain, is also claimed by Vietnam, which fought a deadly naval battle against China in the area in 1988.

AP