Japan's main international gateway, Narita Airport near Tokyo, started testing full-body scanners yesterday as an additional security measure, despite privacy concerns. The transport ministry said it will test five different types of the scanners, which can see through clothing and are made by US, Japanese and European companies and universities, between now and September 10.

"We are asking passengers to volunteer for test scans. We hope to collect 100 samples for each of the machines," Mitsugu Sato, director of the aviation security office at the ministry, said.

"Fortunately, we are receiving many more volunteers than we anticipated." Transport Minister Seiji Maehara said last week he was considering introducing full-body scanners to improve aviation and airport security.

The US has pushed for greater use of the machines, which it said would have stopped a Nigerian man who tried to bring down a US-bound plane last Christmas Day with explosives hidden in his underwear.

Several European countries have tested the technology, including France, Britain and The Netherlands. South Korean airports have also started test programmes.

The machines have remained controversial because of privacy worries, as they generate images of passengers' entire bodies.

In the Japanese tests, the ministry said the scanned images will be neither stored nor transmitted. Images will be viewed only by inspectors of the same gender, the ministry said.