A palm-sized robot dubbed Kirobo Mini has been unveiled in Japan, designed to be a companion for the growing number of women left childless by the country's aging population crisis.

The robot, created by Toyota Motor Corp, aims to emulate a human baby and even "wobbles" like a infant "which hasn't fully developed the skills to balance itself," its chief design engineer Fuminori Kataoka said.

"This vulnerability is meant to invoke an emotional connection," he added.

In the past half century, births in Japan have halved to around one million a year, according to government statistics, with one in 10 women never marrying.

Births out of wedlock are frowned upon in Japan and are much less common than in Western developed nations.

Around a quarter of Japan's population is over 65 with a shortage of care workers putting a strain on social services.

Exacerbated by a reluctance to invite immigrants to bolster its working-age population, Japan's demographic crunch shows little sign of easing, with the Government looking at robots to replenish the thinning ranks of humans.

Senior managing officer Moritaka Yoshida (L) and chief design engineer Fuminori Kataoka (R) unveiled the robots in Tokyo. ( Reuters: Kim Kyung-Hoon )

Kirobo Mini joins growing list of companion robots

The Toyota baby automaton joins a growing list of companion robots, such as the upcoming Jibo, designed by robotics experts at the Massachusetts Institute of Technology that resembles a swivelling lamp, and Paro, a robot baby seal marketed by Japanese company Intelligent System Co Ltd as a therapeutic machine to soothe elderly dementia sufferers.

Japan is already a leading user of industrial robots.

It has the second-biggest concentration after South Korea with 314 machines per 100,000 employees, according to the International Federation of Robots.

Toyota plans to sell Kirobo Mini, which blinks its eyes and speaks with a baby-like high-pitched voice, for 39,800 yen ($AU512) in Japan next year.

Reuters