This file photo taken in February 2012 shows the US guided-missile destroyer Lassen.[Photo/IC]

China said on Tuesday that two of its navy warships sent out warnings after the United States sent a guided-missile destroyer to patrol within 12 nautical miles (22.2 kilometers) of a Chinese island in the South China Sea.

It said the warnings had been sent "in accordance with laws".

Ministry of National Defense spokesman Yang Yujun said in a statement issued on Tuesday night that Beijing "will take all necessary measures to safeguard its own security", and has lodged solemn protests to the US.

The missile destroyer Lanzhou and cruiser Taizhou of the Chinese People's Liberation Army Navy sent the warnings to the US ship, Yang said.

On Tuesday morning, Foreign Minister Wang Yi warned Washington "not to act in an imprudent way and not to make trouble out of nothing".

In the evening, Vice-Foreign Minister Zhang Yesui summoned Max Baucus, the US ambassador to China, and said Beijing strongly urged Washington to "cherish the hard-won virtuous momentum of the China-US relationship and stop taking any action that threatens China's sovereignty and security interests".

Foreign Ministry spokesman Lu Kang confirmed in a statement in the afternoon that the USS Lassen illegally entered waters within 12 nautical miles of Zhubi Reef, which is part of China's Nansha Islands, "without receiving permission from the Chinese government".

Zhang Junshe, a senior researcher at the PLA Naval Military Studies Research Institute, said the warnings were based on international law and were made "within the scope of regular practices and were very professional".

The US action?- quite near to Chinese territory?- threatens not only the country's sovereignty "but also the security of facilities and Chinese personnel stationed on the island", Zhang said.