A US reconnaissance aircraft intentionally intruded on a training area of the Chinese military, undermining regional peace and stability, a spokesman said on Wednesday.

Colonel Zhang Nandong, a spokesperson of the Southern Theater Command, stated a US RC-135 reconnaissance aircraft intentionally entered the training area of a fleet of 17 naval vessels of the Chinese People's Liberation Army in the South China Sea on Friday, conducting reconnaissance. The theater command organized aerial forces to fully track and monitor the aircraft and handled the situation lawfully and professionally, he said.

"The behavior of the US side seriously undermined regional peace and stability and the related reports disregarded the facts, portraying China as the bad actor, which confused right and wrong and the international community," Zhang said.

On Tuesday, the US military said a Chinese fighter jet carried out an "unnecessarily aggressive" maneuver near a US military plane over the South China Sea.

"We sternly urge the US side to effectively restrain the actions of its front-line military forces in the sea and air, strictly abide by international laws and agreements and prevent accidental incidents. Otherwise, the US shall bear all resulting consequences," Zhang said.

"The theater command forces are always on high alert, firmly defending national sovereignty and security and the peace and stability of the South China Sea region."

Foreign Ministry spokesperson Mao Ning said also on Wednesday the US has frequently sent aircraft and vessels to conduct close-in reconnaissance on China.

"Such provocative and dangerous moves are the root cause of maritime security issues," Mao said. "The US should immediately stop such dangerous provocations. We will continue to take necessary measures to firmly safeguard our sovereignty and security."