An official watchdog in Germany has told parents to destroy a talking doll called Cayla because its smart technology can reveal personal data.

BBC reports, the warning was issued by the Federal Network Agency (Bundesnetzagentur), which oversees telecommunications.

Researchers say hackers can use an insecure bluetooth device embedded in the toy to listen and talk to the child playing with it.

Manufacturer Genesis Toys has not yet commented on the German warning.

The Vivid Toy group, which distributes My Friend Cayla, has previously said that examples of hacking were isolated and carried out by specialists. However, it said the company would take the information on board as it was able to upgrade the app used with the doll.

But experts have warned that the problem has not been fixed.

The Cayla doll can respond to a user's question by accessing the internet. For example, if a child asks the doll "what is a little horse called?" the doll can reply "it's called a foal".