Similar systems exist in other European countries, as city administrations struggle to ease both traffic gridlock and air pollution, but the French capital has the most ambitious scheme.

Some 616,000 users have signed up to be able to pick up bikes at more than 750 points in Paris for daily subscriptions of one euro.

"People have taken to the service very quickly. We're getting around 1,200 requests for registration a day," said France Pele from the Paris city hall.

The sturdy grey-green bikes have become a common sight, with people ranging from students to business executives weaving through traffic. Even screen legend Alain Delon has had a go.

"It's very good, I really like it. Although having said that, I can't get this thing to work now," said Roland Martinez, a salesman struggling to clip his bike back into place at a pickup point near the Tuileries gardens.

Paris is unlikely ever to rival classic bicycling cities like Amsterdam. But Velib is a revolution in a city with a vast metro network but an increasingly choked road system, where bicycling has long been looked on with suspicion.

Some 10,000 bikes are already in place and the scheme is set to double in size by the end of the year to include around 20,000 bikes and 1,450 pick up points, one every 300 metres.

The first half hour is free, which organisers believe will cover most users, though longer journeys are possible on a mounting scale of charges. Longer term subscriptions for up to a year are also possible.

The service has not been universally welcomed. Taxi drivers grumble about the numbers of new riders steering these heavy bikes uncertainly down narrow streets, and pedestrians are sometimes forced to dodge riders who take to the pavements.

There have also been problems with keeping an even balance at pickup points, as many users in high-lying districts like Montmartre coast downhill to work in the morning but take the metro home rather than struggling back up the hill.

But authorities believe the problems will be smoothed out.