Recent satellite images show China has made rapid progress in building an airstrip suitable for military use in contested territory in the South China Sea's Spratly Islands and may be planning another, moves that have been greeted with concern in the United States and Asia.

IHS Jane's Defence Weekly said the March 23 images from Airbus Defence and Space showed work on the runway on reclaimed parts of Fiery Cross Reef in the Spratly archipelago, which China contests with the Philippines, Vietnam, Malaysia, Brunei and Taiwan.

It said images from earlier in March showed reclamation work on Subu Reef in the Spratlys creating landmasses that, if joined together, could create space for another 3,000-meter (3,281-yard) airstrip.