Japanese auto giant Nissan on Monday said customers in the United States and Japan had reported problems restarting their all-electric Leaf vehicles after switching the motor off.

"Some customers have reported problems restarting the car after it has stopped," a Nissan spokesman told AFP.

"We are studying the cause of the problem," the spokesman said, adding that the fault posed no accident risk.

Nissan's launch of the Leaf in and the United States in December was seen as a bet on drivers' readiness to embrace the first globally mass-produced electric car.

The Leaf -- short for Leading Environmentally-friendly Affordable Family car -- enjoyed a crescendo of industry buzz in the build-up to its launch and was the first electric vehicle to win European Car of the Year.

The Japanese automaker received 6,000 pre-sale orders in Japan and 20,000 in the United States.

and its French partner Renault have staked their future on and plan to launch several models by 2014 to meet rapidly rising demand for more environmentally-friendly methods of transport.

They have invested four billion euros ($5.7 billion) in the programme.