French riot police secure the Porte Maillot during a demonstration by French taxi drivers, who are on strike, to block the traffic on the Paris ring road during a national protest against car-sharing service Uber, in Paris, France, June 25, 2015. [Photo/Agencies]

Uber, which says it has 1 million users in France, links drivers to passengers via a smartphone app. It has expanded its UberPOP service in French cities, provoking anger from taxi drivers and stirring a debate over what is fair competition.

At Paris Charles de Gaulle airport, staff advised passengers to avoid the traffic chaos by walking between terminals. Dozens of passengers lined the roads, with some scrambling up slopes and across motorway barriers, a Reuters witness said.

French TV showed images of burning tyres blocking part of the Paris ring road and scuffles between cabbies and other drivers. Police in riot gear at one point intervened using tear gas.

Taxi drivers set up barriers around Marseilles and Aix-en-Provence in southeast France, including at motorway exits, and blocked access to train stations in the two cities.

"We are faced with permanent provocation (from Uber) to which there can only be one response: total firmness in the systematic seizure of offending vehicles," G7 taxi firm head Serge Metz told BFM TV.