The images, taken by Planet Labs PBC in early August, show fresh construction on the westernmost island of the Paracel Islands close to Vietnam (and which are claimed by both Vietnam and Taiwan). What has regional and US officials alarmed is the large airstrip which appears to be progressing at rapid pace.

The apparent Chinese military build-up of the island can be seen by comparing these latest satellite images (below) to prior ones.

The Drive was the first to report on and analyze the images, with the publication writing:

The sudden development on the Chinese-controlled Triton Island is revealed in satellite imagery. Clearly, work is still at an early stage, but it's startling just how rapid the progress has been so far. Construction of this airstrip only began a few weeks ago at the most. The War Zone examined imagery from Planet Labs from mid-July showing no such activity.

The new airstrip appears to be over 2000 feet in length according to analysis of the images.

The Drive continues, "As well as the airstrip, satellite imagery reveals a huge new work area, including a cement plant. This has all sprung up within the last month."

"Previously, this Chinese outpost was home to an observation station with two radomes and some big Chinese flags, but not much more. The island was previously served by a small harbor and a helipad," the report added. Chinese state-run Global Times has rejected the allegations.