BEIJING, March 11 (RIA Novosti) - China has lodged an official protest against the U.S. Navy over unauthorized activities in China's exclusive maritime economic zone, the China Daily reported on Wednesday.

The U.S. has also protested over the weekend incident in the South China Sea, saying Chinese ships engaged in dangerous maneuvers when shadowing a U.S. vessel. (VIDEO)

Chinese Foreign Ministry spokesman Ma Zhaoxu told reporters that U.S. vessels, including the USNS Impeccable, conducted illegal surveys on Sunday, 120 kilometers (74.5 miles) to the south of China's Hainan Island.

"China has lodged a protest to the United States, as the USNS Impeccable conducted the activities ... without China's permission," Ma said.

The U.S. Navy insists its actions were in line with international maritime law.

Vice-Admiral Jin Mao, former vice-commander of the People's Liberation Army's (PLA) navy told the China Daily that the U.S. ship was "not a research vessel, but a spy ship."

The Impeccable, which serves with the U.S. 7th Fleet, uses low-frequency sonar to search for undersea threats including submarines.

Chinese Foreign Minister Yang Jiechi is currently in Washington to discuss preparations for the London G20 summit set for April 1to address the financial crisis. Yang is working on plans for a meeting between President Hu Jintao and U.S. President Barack Obama during the summit.

The naval incident may be discussed by Yang and U.S. Secretary of State Hillary Clinton during the Chinese diplomat's visit.