China demands end to US surveillance of its backyard

China demanded an end to US surveillance near its territory on Thursday after two of its fighter jets carried out what the Pentagon said was an "unsafe" intercept of a US military reconnaissance aircraft over the South China Sea.

The incident, likely to increase tension in and around the contested waterway, took place in international airspace on Tuesday as the plane carried out "a routine US patrol," a Pentagon statement said.

A US defence official said two Chinese J-11 fighter jets flew within 50 feet of the US EP-3 aircraft. The official said the incident took place east of Hainan Island. "Initial reports characterized the incident as unsafe," the Pentagon statement said. (See: Chinese jets make 'unsafe' intercept of US spy plane). "It must be pointed out that US military planes frequently carry out reconnaissance in Chinese coastal waters, seriously endangering Chinese maritime security," China's foreign ministry spokesman Hong Lei Hong told reporters.

"We demand that the United States immediately cease this type of close reconnaissance activity to avoid having this sort of incident happening again," Hong said.

Speaking at a regular press briefing, he described the Pentagon statement as "not true" and said the actions of the Chinese aircraft were "completely in keeping with safety and professional standards".

"They maintained safe behaviour and did not engage in any dangerous action," Hong said.

The encounter comes a week after China scrambled fighter jets as a US Navy ship sailed close to a disputed reef in the South China Sea.

Another Chinese intercept took place in 2014 when a Chinese fighter pilot flew acrobatic manoeuvres around a US spy plane.

The intercept occurred days before President Barack Obama travels to parts of Asia from 21-28 May, including a Group of Seven summit in Japan and his first trip to Vietnam.

China claims most of the South China Sea, through which $5 trillion in ship-borne trade passes every year and which is also considered rich in energy deposits. The Philippines, Vietnam, Malaysia, Taiwan and Brunei have overlapping claims.

Washington has accused Beijing of militarising the South China Sea after creating artificial islands, while Beijing, in turn, has criticized increased US naval patrols and exercises in Asia.