A knee-high, black-and-white buggy rolls down a snowy pavement in Estonia's capital Tallinn and, carefully avoiding pedestrians, stops obediently at the red traffic light of a large road junction.

The six-wheeled robot, on its way to deliver lunch to a client, knows to cross only when the pedestrian light is green, but, armless, it cannot press the traffic light button.

Inventors Starship Technologies have taught their robots to avoid traffic lights with buttons and are now giving them speakers and microphones to help them navigate pedestrian crossings. While not quite as talkative as C-3PO, the quick-witted droid of "Star Wars" movies, Starship robots will be able to communicate with humans.

"We'll have predefined sentences that are used in certain situations. Like 'hello' or... 'could you press the button of the traffic light'," Mikk Martmaa, the 26-year-old head of Starship's testing program in Estonia, told AFP.

Most passers-by smile as the robot resembling a hi-tech icebox roams the streets of Tallinn's Mustamae district.

"I've seen the Second World War and now I've lived to see robots on the streets of Tallinn!," marvels 80-year-old resident Aleksandra Vaskina.

A prototype of the robot was first designed for a NASA competition seeking bots able to collect rock samples on Mars or the Moon. While it did not win, the Tallinn-based engineers behind the model thought it was perfect for food deliveries.

To explore the idea, lead engineer Estonian Ahti Heinla and Denmark's Janus Friis, co-founders of the online call service Skype, created Starship Technologies in London in 2014. The startup's bots are being developed and tested in the Baltic state of Estonia, one of the world's most wired countries and a trailblazer in new technology.

On a cold February day, 27-year-old TV producer Liisi Molder does not feel like going out but fancies a 12-euro ($13) portion of squid and celeriac with herring roe and rocket in shellfish sauce from the busy nearby Umami restaurant.