A US firm has begun implanting microchips the size of a grain of rice in its employees.

Three Square Market, a technology firm in Wisconsin, said 50 of its employees had voluntarily signed up to have the Radio-Frequency Identification technology fitted form August.

Implanted between the thumb and forefinger it will allow them to pay for snacks when they are on a break among other functions.

In a statement Chief Executive Officer Todd Westby said: "We foresee the use of RFID technology to drive everything from making purchases in our office break room market, opening doors, use of copy machines, logging into our office computers, unlocking phones, sharing business cards, storing medical/health information, and used as payment at other RFID terminals,"

"It's the next thing that's inevitably going to happen, and we want to be a part of it." He added: "Eventually, this technology will become standardised allowing you to use this as your passport, public transit, all purchasing opportunities."

The technology is the same sis is used to pay for items using mobile phone scans.

Employees will not be required to have the implants and the company will pay for the microchips which cost $300 each.