While city centres were closed to private cars, the authorities tried to encourage five million city residents and workers to use alternative means of transport.

Pollution levels in the country have been rising alarmingly in recent years, and the government is seeking to wean the public away from its dependence on the car.

In Paris, 28 zones were declared traffic free from early morning, affecting about 60km of the capital's streets.

Only emergency vehicles - buses, taxis, fire engines, ambulances, police cars, rubbish trucks - and those powered by gas or electricity remain exempt from the ban.

Some 1,000 bicycles were available for rent from the City Hall.

Paris Mayor Jean Tiberi reported a 20% cut in traffic during the day and a 65% increase in cyclists using the central rue de Rivoli and Boulevard Saint-Germain.

But other city administrations, including some of France's biggest cities, ignored the ministry's directive, or re-arranged their car-free days for a Sunday.

Under the initiative organised by the French environment ministry, exhibitions and other cultural events were staged while the cars stayed at home.

Across the country, special fares were on offer in operation on public transport, exhibitions will show the effect of pollution on people and buildings, and new non-polluting types of transport will be on display.

Public opinion polls show strong support for the principle of closing city centres to traffic, though in practice, the move might prove less popular.