IN PHOTOS: China's reclamation on Mabini Reef

MANILA, Philippines - The Department of Foreign Affairs (DFA) on Monday released photos of China's construction efforts on Philippine-claimed Mabini (Johnson South) Reef in the disputed South China Sea.

DFA said the photographs showing China's "extensive reclamation" were gathered from Philippine intelligence sources.

"These actions are considered destabilizing and in violation of the Declaration on the Conduct of Parties in the South China Sea (DOC) and international law. Mabini Reef is part of the Kalayaan Island Group (KIG) which is part of Philippine territory," DFA said in a statement.

The aerial shots show the development of the construction from March 2012 to March 2014.

On Wednesday, Foreign Affairs Secretary Albert del Rosario announced that the Philippines has filed a protest in April against what appeared to be building activities leading to the construction of an airstrip.

"We're not exactly sure what are their intentions are," Del Rosario said.

China, however, rejected the protest and insisted on its rights to engage in construction on the reef, which the Philippines claims as part of Palawan province

"I wonder what special motives there are behind such concerns by the Philippines," China Foreign Ministry spokeswoman Hua Chunying said at a news conference in Beijing.

The Philippine government estimates that the reclamation has turned the submerged reef and a sand bar into a 30-hectare (74-acre) land mass that transformed the underwater outcrop into an islet.

Where is  Mabini Reef?

Johnson South Reef, located in a vast, bean-shaped submerged coral outcrop, is also claimed by Vietnam, which maintains several nearby military installations. Chinese and Vietnamese forces fought a deadly naval battle in the contested region in 1988.

Located about west Puerto Princesa City, Palawan, the China-controlled feature lies near Vietnam-occupied Collins Reef.