A US Navy destroyer sailed within 12 nautical miles or within the territorial waters of an island claimed by China in the South China Sea, in a sign of increasing tension in the region days after Secretary of State John Kerry visited Beijing attempting to settle long standing territorial disputes. Taiwan and Vietnam also have claims to the island as well.

The guided missile destroyer USS Curtis Wilbur (DDG-54) conducted a freedom of navigation operation Saturday near Triton Island, part of the Paracel Island chain in the South China Sea, a Pentagon spokesman confirmed to Fox News. There were no Chinese warships in the area at the time and the transit was characterized as “innocent.”

“This operation was about challenging excessive maritime claims that restrict the rights and freedoms of the United States and others, not about territorial claims to land features,” said Capt. Jeff Davis, a Pentagon spokesman.

Davis said none of the three claimants to the island were notified before the US Navy warship transited the area as part of a “normal process” supported by international law. Davis refused to single out China specifically.

Tension in the region has been building for months.

In October, another US Navy destroyer, USS Lassen, conducted a patrol within 12 nautical miles of another Chinese island, a disputed man-made island in the South China Sea part of the Spratly chain of islands, drawing a strong rebuke from China.

In November US Air Force B-52 bombers flew near other contested Chinese islands. The following month, the U.S. military deployed a U.S. Navy P-8 Poseidon reconnaissance plane to Singapore.

Earlier this month, China landed a pair of civilian airliners to test a newly constructed airstrip atop Fiery Cross reef, which the Chinese have converted into an artificial island in the South China Sea. US defense officials believe military jets could be coming soon.