Airbus Defence and Space imagery dated 14 November 2014 shows Chinese land reclamation operations under way at Fiery Cross Reef in the South China Sea. Multiple operating dredgers provide the ability to generate terrain rapidly. Operating from a harbour area, dredgers deliver sediment via a network of piping. (© CNES 2014, Distribution Airbus DS / Spot Image / IHS) HONG KONG (Reuters) - China's creation of artificial islands in the South China Sea is happening so fast that Beijing will be able to extend the range of its navy, air force, coastguard and fishing fleets before long, much to the alarm of rival claimants to the contested waters.

Reclamation work is well advanced on six reefs in the Spratly archipelago, according to recently published satellite photographs and Philippine officials. In addition, Manila said this month that Chinese dredgers had started reclaiming a seventh.

While the new islands won't overturn U.S. military superiority in the region, Chinese workers are building ports and fuel storage depots as well as possibly two airstrips that experts said would allow Beijing to project power deep into the maritime heart of Southeast Asia.

"These reclamations are bigger and more ambitious than we all thought," said one Western diplomat. "On many different levels it's going to be exceptionally difficult to counter China in the South China Sea as this develops."

China claims most of the potentially energy rich South China Sea, through which $5 trillion in ship-borne trade passes every year. The Philippines, Vietnam, Malaysia, Brunei and Taiwan also have overlapping claims.

All but Brunei have fortified bases in the Spratlys, which lie roughly 1,300 km (810 miles) from the Chinese mainland but much closer to the Southeast Asian claimants.

Beijing has rejected diplomatic protests by Manila and Hanoi and criticism from Washington over the reclamation, saying the work falls "within the scope of China's sovereignty".

The Philippines began expressing growing concern in mid-2014, in particular, accusing Beijing of building an airstrip on Johnson South Reef.

Satellite analysis published by IHS Jane's Defence Weekly this week showed a new installation being built on Hughes Reef. It described a "large facility" having been constructed on 75,000 square meters of sand reclaimed since August.

It also published images of Fiery Cross Reef, which now includes a reclaimed island more than 3 km (1.8 miles) long that experts said would likely become a runway.

Work is also well established on Gaven, Cuarteron and Eldad Reefs, with the new dredging taking place on Mischief Reef.

Boon for fisherman

While the prospect of China using the artificial islands to refuel warplanes in any conflict was a possibility, some experts highlighted significant non-military benefits.

China could keep its fishing fleets and coastguard working in Southeast Asia more effectively, with crews able to re-supply and rest, said Carl Thayer, a South China Sea expert at Canberra's Australian Defence Force Academy. Oil explorers would similarly benefit.

Reuters reported in July that Chinese authorities were encouraging fishermen to sail to the Spratlys, often providing fuel subsidies to help.

Before the reclamation, China's facilities were limited to squat buildings and radar domes built on rocky outcrops, with limited berthing and storage facilities, a contrast to natural islands occupied by Taiwan and the Philippines.

"Even before you factor in military questions, the expansion of Chinese fishing and coastguard fleets is going to be a strategic shift that is going to be very hard for anyone to counter," said Thayer.

"And then you will have the navy just over the horizon." A Chinese navy sailor (R) guides a helicopter to land on Chinese destroyer Harbin during the Joint Sea-2014 naval drill outside Shanghai on the East China Sea, May 24, 2014. Chinese and Russian navies staged exercises on the East China Sea on Saturday to simulate anti-submarine and search-and-rescue operations. A total of 14 surface ships, two submarines, nine fixed-wing warplanes, six shipboard helicopters and two operational detachments are taking part in this year's week-long drill, state media reported. Picture taken May 24, 2014. REUTERS/China Daily

Thayer noted that while no legal claim could be extended from an artificial island, China would effectively move to force rival countries from the surrounding seas.

Chinese strategic analysts said the build-up was being driven by what Beijing sees as security threats, especially the need to check Vietnam, which has had up until now the most holdings in the Spratlys, with 25 bases on shoals and reefs. Vietnam is also quietly building up its submarine fleet to counter China.

The two Communist Party-ruled neighbors clashed at sea in 1988 when China took its first Spratly holdings, including Fiery Cross Reef, from Vietnam.

Some regional military attaches believe China may eventually use helicopter facilities on the new islands to run anti-submarine operations.

"This is less about politics and legal issues and more about security, from China's perspective," said Zhang Baohui, a mainland defense specialist at Hong Kong's Lingnan University.

Strategic Gap

Gary Li, an independent security analyst in Beijing, said he believed any military pay-off would be relatively small from the new islands, given their distance from the Chinese mainland.

"I suspect these reclamations would only ever have localized tactical uses in military terms," Li said. A Chinese vessel works on a building project in the Spratly Islands in 2014. AFP

China's lack of offshore military bases and friendly ports to call on was apparent last year when Chinese naval supply vessels sailed to Australia to replenish warships helping look for a missing Malaysian airliner in the Indian Ocean.

Naval planners know they will have to fill this strategic gap to meet Beijing's desire for a fully operational blue-water navy by 2050.

More immediately, some analysts said they believed the islands would give China the reach to create and police an air defense identification zone (ADIZ) above the South China Sea.

China sparked condemnation from Japan and the United States when it imposed an ADIZ, where aircraft are supposed to identify themselves to Chinese authorities, above the East China Sea in late 2013. China has denied speculation it would follow suit in the South China Sea.

Roilo Golez, a former Philippine national security adviser, predicted China would complete its reclamation work by early next year and announce an ADIZ within three years.

"They are connecting the dots. They're putting real muscle into this," Golez said.

(Additional reporting by Manny Mogato in MANILA and Michael Martina in BEIJING; Editing by Dean Yates)