Pentagon spokesman Captain Jeff Davis said on Saturday that the guided-missile destroyer, USS Curtis Wilbur, sailed within 12 nautical miles of Triton Island in the Paracel Islands.

"This operation challenged attempts by the three claimants - China, Taiwan and Vietnam - to restrict navigation rights and freedoms," Davis said.

Current policy in the South China Sea requires prior permission or notification of transit within territorial waters.

Territorial violation

China's foreign ministry said shortly after the operation that the warship had violated Chinese law by entering its territorial waters "without prior permission."

"The Chinese side has taken relevant measures including monitoring and admonishments," China's foreign ministry added in a statement.

Davis said earlier, however, that no Chinese military ships were in the vicinity of the US warship when it passed the artificial island.

China's controversial land reclamation project in the South China Sea has ignited tensions in the region in recent months, particularly with Vietnam and the Philippines, who have made overlapping claims to the area. Some $5 trillion (4.62 trillion euros) of ship-borne trade passes through the waters every year.

The operation on Saturday came in light of recent criticism towards US President Barack Obama for delaying further freedom of navigation patrols in the South China Sea.

ksb/gsw (Reuters, AFP)