Digital advertising billboards being trialled in Japan are fitted with cameras that read the gender and age group of people looking at them to tailor their commercial messages.

The technology - reminiscent of the personalised advertisements in Steven Spielberg's sci-fi movie Minority Report - forms part of the Digital Signage Promotion Project, which is currently in a test phase.

A consortium of 11 railway companies launched the one-year pilot project last month and has set up 27 of the high-tech advertising displays in subway commuter stations around Tokyo.

"The camera can distinguish a person's sex and approximate age, even if the person only walks by in front of the display, at least if he or she looks at the screen for a second," said a spokesman for the project.

If data for different locations is analysed, companies can provide interactive advertisements "which meet the interest of people who use the station at a certain time," the project said in a statement.

While in Minority Report advertisers recognise individuals such as Tom Cruise's character by name and make purchasing suggestions, the Japanese project does not identify people and only collates demographic data.

The technology uses face recognition software to glean the gender and age group of passers-by, but operators have promised they will save no recorded images, only the collated data about groups of people.