China has not ruled out the possibility of installing body scanners at major airports, a top civil aviation official said.

The Civil Aviation Administration of China (CAAC) is still considering the pros and cons of the body scanner, since it involves passengers' privacy, Li Jiaxiang, head of CAAC, has revealed.

"It is our concern that while we must ensure flight safety, passengers should not feel deprived of dignity or freedom when going through security checks," he said.

A girl takes off her shoes to receive security check in the airport in Xi'an, west China's Shaanxi province.

The United States has announced plans to install full body scanners at all its major airports following a foiled Christmas Day bid to blow up a Northwest Airlines flight from Amsterdam to Detroit. So far, media reports said 19 American airports already use at least one such scanner.

Meanwhile, in Europe, Britain, the Netherlands and Italy are among countries that have announced plans to use full-body scanners.

The use of these machines, which cost $200,000 each, has sparked a heated debate over privacy, because scanning penetrates packaging and clothing, and produces "naked" images of passengers.

But, no matter how advanced the security-check measures are, it is not possible to close every loophole, Chinese counter-terrorism expert Li Wei said.

"Machines are operated by people, and people could get tired or not be alert enough," said Li, who is director of the center for counter-terrorism studies at the China Institute of Contemporary International Relations.