A coral reef area in the South China Sea that was almost entirely submerged has been transformed into a massive artificial island stretching 6 kilometers long.

The ultra-large artificial island was constructed by China, and with the addition of a harbor capable of accommodating warships, analyses suggest that China is securing yet another military stronghold in the South China Sea.

Reuters released satellite imagery of Antelope Reef in the Paracel Islands, captured by commercial satellite imagery firm Vantor.

Originally a coral reef zone mostly submerged underwater, it has been transformed into a C-shaped artificial island spanning nearly 6 kilometers through reclamation work mobilizing dredging vessels and barges over a period of at least six months.

Inside the island, a harbor and piers where ships can dock have also been built.

The pier alone is approximately 680 meters long, and satellite photos taken in June captured a China Coast Guard vessel docked there.

Experts are paying close attention to the strategic value of Antelope Reef.

The northern part of the South China Sea where it is located is a strategic bottleneck connecting the Chinese mainland, Taiwan, and the South China Sea.

Ben Lewis of PLA Tracker, a private military analysis organization that tracks the movements of the Chinese military, analyzed that if a conflict arises surrounding Taiwan, Antelope Reef could serve as one of the Chinese military's key strategic strongholds.

There are also projections that it could be utilized as a sort of maritime fortress to protect China's strategic nuclear submarines.

While China has not officially acknowledged that it is building a new military base, Reuters evaluated that with the completion of this reclamation project, the South China Sea is increasingly turning into a military stage.

Territorial disputes are also expected to intensify further.

China has exercised effective control over the entire Paracel Islands since driving out South Vietnamese forces in 1974.

However, Vietnam still claims sovereignty over the entire Paracel Islands.

The Vietnamese government reaffirmed its position that it is its territory, stating its firm opposition to China's development of Antelope Reef back in March.

Reported by Kim Minjeong | Video by Jang Yujin | Graphics by Yook Do-hyun | Produced by SBS Digital News