Beijing announced Tuesday that it has begun operating a lighthouse on the man-made island in the contested South China Sea that the U.S. sailed a warship near last October as part of its so-called freedom of navigation program.

The completion of the lighthouse on Subi Reef in the disputed Spratly archipelago comes amid growing tensions with other regional claimants as well as the U.S. and Japan over Beijing's aggressive moves in the South China Sea.

Some observers have expressed concern that having lighthouses in the disputed waters could boost Beijing's claim of sovereignty over the region, which the U.S. and its allies say is being militarized by China.