While this operation had been planned months in advance, and similar operations have become routine, it comes at a particularly sensitive time and just days after the Pentagon uninvited China from a major US -hosted naval drill.
The two warships, the USS Antietam, a guided-missile cruiser home-ported in Yokosuka, Kanagawa Prefecture, and the USS Higgins, a destroyer, had "arbitrarily entered China's territorial waters around the Xisha Islands without permission of the Chinese government", spokesman Wu Qian said, using the Chinese name for the Paracels.
The military vessels carried out manoeuvring operations near Tree, Lincoln, Triton and Woody islands in the Paracels, a U.S. official said on condition of anonymity.
Critics of the United States naval operations have said that they have little impact on Chinese behaviour and are largely symbolic.
China's military took "immediate action" on Sunday against "unauthorized" sailing by USA warships in South China Sea waters claimed by Beijing.
"We conduct routine and regular Freedom of Navigation Operations (FONOPs), as we have done in the past and will continue to do in the future", the U.S. Pacific Fleet said in a released statement.
In a statement, the ministry said the military immediately dispatched naval ships and aircraft to "warn them off".
It claimed the United States had entered the country's territorial waters without permission.
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London's Metropolitan Police and Los Angeles prosecutors have said they are reviewing accusations of sexual assault against him. Vance made the decision even though he had a covert police recording of Weinstein telling Gutierrez he would not do it again.
A statement released by the Chinese Ministry of Defense condemned the operation, saying that it had "contravened Chinese and relevant global law, seriously infringed upon Chinese sovereignty [and] harmed strategic mutual trust between the two militaries".
The Philippines has notified China of its "red lines"-potential Chinese actions that would be unacceptable to Manila-in the South China Sea, including oil and gas extraction in disputed areas, the Philippine Foreign Secretary Alan Peter Cayetano said on Monday".
China said "mutual trust between the two militaries" had been "harmed" as a result, and that it would "continue to take all necessary measures to defend the country's sovereignty and security". If anyone gets the natural resources in the Western Philippines Sea, South China Sea, he will go to war.
Earlier in the month, the USA also formally protested against the deployment of missiles and radar equipment on three artificial islands China has built in the Spratly islands.
The U.S. had included China in the past two versions of the naval exercise known as Rim of the Pacific, or RimPac, in 2014 and 2016.
Earlier in May, the U.S. chose to cancel its invitation to China to participate in the maritime 2018 Rim of the Pacific (RIMPAC) drills because of the South China Sea's "militarization", after several Chinese Air Force bombers landed on islands and reefs in the area.
But China will miss out on the exercises this year, which are held in Hawaii, following Mattis' decision.
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