A MASKED-UP Hyundai prototype has been spotted displaying an engine bay full of heavy-duty electrical hardware, confirming that development is well underway for the company’s first mid-sized hybrid.

Underneath the heavy camouflage lies the 2011 Hyundai Sonata, due to be unveiled at the Detroit Auto Show in January 2010.

Hyundai is expected to revitalise the Sonata with a new four-door coupe body, and, as these spy photos show, the new Sonata will look a great deal more upmarket as a result.

The 2011 Sonata won’t be Hyundai’s first hybrid - that honour goes to the Elantra LPi Hybrid launched in Korea last month - but it will be its first mass-market petrol-electric vehicle.

Although primarily targeted at the US market, the Sonata hybrid stands a strong chance of eventually coming to Australia.

In addition to the hybrid powertrain, the 2011 Sonata is expected to make use of a number of direct-injected petrol inline-fours and a range-topping V6.

GALLERY » 2011 Hyundai Sonata Hybrid Spy Photos