The group that runs Paris car-sharing scheme Autolib' said Tuesday it had filed a criminal complaint accusing German carmaker BMW of using spies to gather information on its electric cars.

The Bollore group said it had filed the industrial espionage complaint after two employees of a firm employed by BMW were spotted three times tampering with charging points and Autolib' vehicles parked in Paris.

BMW denied any wrongdoing.

"We do not know for now what information they have been able to gather or the technologies that they have used," Autolib' spokesman Jules Varin told AFP.

"All we can say is that Bollore is ahead in several technologies in which we have invested a lot of money, including the battery and the geo-location system," he said.

A judicial source confirmed that Autolib' had taken legal action.

BMW says the two workers, employed by engineering firm P3 to prepare the launch for the upcoming "i3" electric model, were "conducting routine tests carried out across Europe to check the compatibility of charging points on public roads."

The two men aroused suspicions when they were found tampering with a Bollore Bluecar -- as the electric model is called -- on August 21 in a charging point in the city's 9th district.

When questioned by Autolib' staff, they replied in halting French that they worked for a German carmaker. They gave no name but were driving a BMW car registered in Germany.

The next day they were spotted at another charging point but the Autolib' maintainance staff could not apprehend them. They were finally caught on September 5 in the city's 7th district and arrested.

The duo were questioned by police but released the following day.

BMW said they had ordered the tests to be carried out in the first two cases the duo was spotted but not on the last day when they were arrested.

The Autolib' service was started in December 2011 and deploys all-electric cars for public use on a paid subscription basis, based around a citywide network of parking and charging stations.

The succesful scheme currently has 34,000 subscribers, 1,800 vehicles and around 4,000 charging points in the French capital and its suburbs, and has been extended to other cities such as Lyon and Bordeaux.

There were nearly 6,000 electric cars registered in France last year, of which a third were Autolib' vehicles, according to the Bollore group.