Latest satellite images of the disputed South China Sea show the presence of reinforced aircraft hangars built by China on three specific locations, which could mean the country is preparing for a military deployment, a report by the Centre for Strategic and International Studies (CSIS) said. Experts believe that the size of the hangars is just apt for Chinese fighter jets.

Tensions over the South China Sea have grown since The Hague court ruled in July that China's maritime claims are illegal.

The satellite images that were taken in late July – a few weeks after The Hague ruling came – showed hangars have been constructed on the disputed waters of Fiery Cross, Subi and Mischief Reefs in the Spratly islands. The Washington-based research group's report stated that although there has been no evidence so far of any military deployment by China in the South China Sea, the images indicate an imminent militarisation in the area.

The images have also cast doubts on President Xi Jinping's assurance given to US President Barack Obama in September 2015 that the country had no plans to "pursue militarisation" in the Spratly islands.

"Except for a brief visit by a military transport plane to Fiery Cross Reef earlier this year, there is no evidence that Beijing has deployed military aircraft to these outposts. But the rapid construction of reinforced hangars at all three features indicates that this is likely to change. Each of the three islets will soon have hangar space for 24 fighter-jets plus 3-4 larger planes," the centre stated in its report.

"The smallest and most numerous hangars are being built with four to six hangars per building. They can easily accommodate any fighter-jet in the People's Liberation Army Air Force (PLAAF), including the J-11 and Su-30."

The report added: "The second type of hangar is large enough for the H-6 bomber and H-6U refueling tanker, Y-8 transport aircraft, and KJ200 Airborne Warning and Control System plane. The largest of the hangars can accommodate the largest planes in the PLAAF fleet—the Y-20 and Il-76 transport planes, Il-78 refuelling tanker, and KJ-2000 surveillance aircraft."

South China Sea dispute
Latest satellite images of South China Sea taken late in July show China's construction of aircraft hangars on the disputed Spratly islandsReuters

Responding to the report on the reinforced hangars, China's Defence Ministry said the country has "indisputable sovereignty over the Spratly islands and nearby waters".

"China has said many times, construction on the Spratly islands and reefs is multipurpose, mixed, and with the exception of necessary military defensive requirements, are more for serving all forms of civil needs," the ministry told Reuters.

Although China has been asserting that constructions on the Spratly islands, locally referred to as the Nansha Islands, are for civilian purposes, experts believe that the country is evidently prepping up for military deployment – either for a robust defence or as a display of its power.

The CSIS report also mentioned about some "unidentified hexagonal structures" that were being built quickly at four locations on each islet "always oriented toward the sea". Construction of these structures began in May at Fiery Cross and in July at Subi and Mischief.

Each of these structures have a set of three towers, one of which is larger than the other two, but the towers do not have domes to indicate radar or other sensitive arrays. "These structures do not appear at any of China's other outposts in the Paracels or Spratlys," the report said.