Dec. 11 (UPI) -- Vietnam has quietly accelerated land reclamation at South Reef, a once-remote coral feature in the contested Spratly Islands, signaling a new strategic turn as pressure from China intensifies across the South China Sea.

New satellite imagery reviewed by analysts shows significant dredging, reinforced embankments and the early formation of what appears to be a sheltered harbor and logistics zone.

South Reef,- known in Vietnamese as Đá Nam, has long been one of Hanoi's lesser-developed outposts. But the latest construction suggests Vietnam is moving to harden a chain of positions that could strengthen surveillance, resupply and defensive coordination across the southern Spratlys.

"Vietnam has been quietly expanding multiple features for years, but the work at South Reef stands out," said Gregory Poling, director of the Asia Maritime Transparency Initiative at the Center for Strategic and International Studies.

"This is part of a broader effort to ensure Vietnam isn't outmatched by China's overwhelming presence," Poling said.