By David Brunnstrom
WASHINGTON (Reuters) - Newly released satellite images show Vietnam has carried out significant land reclamation at two sites in the disputed South China Sea, though the scale and pace of the work is dwarfed by that of China, a U.S. research institute said on Thursday.
The photographs, shared with Reuters by Washington's Center for Strategic and International Studies (CSIS), show an expansion of the land area of Vietnamese-controlled Sand Cay and West London Reef in the Spratly archipelego and the addition of buildings.
Mira Rapp-Hooper, director of CSIS's Asia Maritime Transparency Initiative, said the work included military installations and appeared to have started before China began a flurry of reclamation projects last year.
The photographs, taken by satellite imagery firm DigitalGlobe, were taken between 2010 and April 30 this year.
"On one site, it has constructed a significant new area that was formerly under water and at another it has used land reclamation to add acreage to an existing island," Rapp-Hooper said.
The speed of recent Chinese reclamation work has alarmed its neighbors and the United States, which sees it as a potential threat to the status quo in a region through which $5 trillion of sea-borne trade passes each year.
China claims 90 percent of the South China Sea, which is thought to be rich in oil and gas, with overlapping claims from Brunei, Malaysia, the Philippines, Vietnam and Taiwan.
New Vietnamese military facilities at Sand Cay appeared to include defensive positions and gun emplacements, and new buildings visible on West London Reef could also have military applications, Rapp-Hooper said.
Late last month, after weeks of criticism about its reclamation work, China hit back by accusing Vietnam, the Philippines and others of carrying out illegal building work on "Chinese" islands in the South China Sea.
"Strictly speaking, these photos show that China is right," Rapp-Hooper said, "but we can safely say that the scope and scale of what China has undertaken is totally unprecedented and dwarfs Vietnam’s activities many times over."
She said the images showed that Vietnam had reclaimed about 65,000 square meters (699,654 square feet) of land at West London Reef and 21,000 square meters (226,042 square feet) at Sand Cay. This compared to 900,000 square meters (9.6 million square feet) reclaimed by China at a single reef, Fiery Cross.
Rapp-Hooper said satellite images showed that since about March 2014, China had conducted reclamation work at seven sites in the Spratlys and was constructing a military-sized air strip on one artificial island and possibly a second on another.
She said Vietnam already had an airstrip on the Spratlys.
The U.S. State Department and Pentagon had no immediate comment on the latest images.
U.S. President Barack Obama last month accused China of "flexing its muscles" to advance its maritime claims and Washington has been helping countries in the region, including Vietnam, strengthen their defense capabilities.
(Reporting by David Brunnstrom; Editing by Warren Strobel and Stuart Grudgings)