China's defence ministry has protested against what it called "provocation" after US warships sailed near South China Sea islands claimed by Beijing.
US officials, speaking on condition of anonymity, told the Reuters news agency that two military vessels came within 12 nautical miles (around 22km) of the disputed Paracel Islands, among a string of islets, reefs and shoals over which China has territorial disputes with its neighbours.
The Higgins guided-missile destroyer and the Antietam, a guided-missile cruiser, carried out manoeuvering operations near Tree, Lincoln, Triton and Woody islands in the Paracels, one of the officials said.
In a statement later on Sunday, China's defence ministry said the move "contravened Chinese and relevant international law, seriously infringed upon Chinese sovereignty (and) harmed strategic mutual trust between the two militaries".
It also said it had deployed ships and aircraft to warn the US warships to leave, saying they had entered the country's territorial waters without permission.
In a separate statement, China's foreign ministry urged Washington to stop such actions.
"China will continue to take all necessary measures to defend the country's sovereignty and security," it added, without elaborating.
The US military did not immediately comment on the operation, but said US forces operate in the region on a daily basis, Reuters said.
South China Sea standoff China is pitted against smaller neighbours in multiple disputes in the South China Sea over islands, coral reefs and lagoons in waters crucial for global trade and rich in fish and potential oil and gas reserves.
It has begun building military structures on disputed islands - much to the dismay of other Southeast Asian nations including the Philippines, Indonesia, Malaysia, Taiwan and Vietnam.
The incident on Sunday came on the heels of a string of events that highlight tension between the world's two biggest economies over the South China Sea's disputed waters.
On Wednesday, the Pentagon withdrew an invitation to China to participate in the world's largest multinational maritime exercise in a move the Chinese defence ministry called "not constructive".
The Pentagon said its decision was "an initial response to China's continued militarisation of the South China Sea".
Earlier this month, China's air force landed long-range military aircraft on Woody Island, marking the first time a strategic bomber landed on an island in the South China Sea.