BEIJING, Nov. 29 -- Planes from the People's Liberation Army (PLA) Air Force have the right to patrol in China's East China Sea Air Defense Identification Zone (ADIZ) in light of the need of air defense, said a Foreign Ministry spokesman on Friday.

Qin Gang made the remarks at a regular press briefing when asked to explain the purpose of the PLA Air Force's patrol in the ADIZ on Thursday.

China's armed forces shoulder the mission of protecting the country and safeguarding peace, he said, noting that the armed forces are permanently in a state of high alertness.

China announced the establishment of the ADIZ last Saturday, requiring aircraft to report their flight plans and identify themselves while flying through the zone.

Qin urged reporters to make a distinction between the ADIZ and airspace, noting that the former, which is demarcated outside territorial airspace, is not exclusive.

According to international laws, the normal flight of aircraft of other countries will not be affected, he said, adding that the measures adopted in China's airspace will not be extended to the ADIZ.

Order and freedom of flight over the East China Sea have not been affected since the establishment of the ADIZ, according to the spokesman.

Responding to questions on China's requirement of flight plan identification in the zone, Qin said since there are no specific provisions in international laws in this aspect, China's demand does not violate international laws and conforms to international practices.

More than 20 countries, including the United States, Japan and Australia, have set up their own air defense identification zones since the 1950s.