TOKYO (Reuters) - Colourful nano-drones, described by designers as the world's smallest flying drone, proved a big crowd puller at the International Tokyo Toy Show this week.

The smallest drone was 3.5cm wide and weighed 9g, although a heavier 11g version was equipped with a camera able to film four minutes of video in flight.

The green, pink and blue remote controlled nano-drones cost between US$60 (S$81) and US$100 and were light enough that they do not require a permit to fly in Japan.