China's objection expressed by its Foreign Ministry spokesman Hong Lei comes after South Korea announced its decision to expand its air defense zone in response to China's recent surprise announcement of setting up a similar zone in the East China Sea, overlapping the existing zones of South Korea and Japan.
The United States has already welcomed South Korea's move, saying Seoul is pursuing the issue in a responsible way with prior consultations with the Washington and its neighbors including China and Japan.
However, China's official Xinhua News Agency quoted Foreign Ministry spokesman Hong as saying Beijing had expressed regret over South Korea's action as it encompassed submerged rocks within the overlapping exclusive economic zones of South Korea and China.
Hong, however, acknowledged China and South Korea have maintained communication, adding Seoul should "cautiously and properly handle the issues," Xinhua said.
"China is ready to maintain communication with (South Korea) in line with the principle of equality and mutual respect," Hong added.
Seoul has said its zone was expanded further south to encompass the South Korea-controlled Ieodo reef in the sea, which China refers to as Suyan.
Explaining the decision, South Korean President Park Geun-hye said, "As a sovereign nation, we prudently made the decision in order to maximally guarantee our national interests after conducting in-depth reviews among related agencies and collecting opinions from various circles," Yonhap News reported.
She said tensions are escalating with the rapidly changing situation in the Northeast Asia region.
"Every one of these issues is an important matter that can affect the future of our country," Park said. "The government is doing its best to stably manage the situation under the consistent principles of putting national interests ahead of anything else and building trust."
The Chinese zone announcement already has been strongly opposed by the United States and its allies, which have refused to recognize it. U.S. Vice President Joe Biden, during his visit to Beijing last week, urged Chinese leaders not to implement the zone.
At her media briefing Monday, U.S. State Department spokeswoman Jean Psaki said the South Koreans were not creating a new zone but only adjusting it, adding Seoul pursued its action in a responsible, deliberate fashion by prior consultations not only with the United States, but importantly, with Japan and China.
"That was not a step, as you know, that was taken by China," she said. "We also appreciate (South Korea's) commitment to implement this adjustment in a manner consistent with international practice and respect for the freedom of overflight and other internationally lawful uses of international airspace."
Additionally, Psaki said the South Korean zone adjustment "doesn't encompass territory administered by another country, which was another area that had drawn some concern from our end related to the China ADIZ."