French riot police and firefighters cleared a busy Paris ring road at rush-hour on Tuesday after taxi drivers angry about competition from private car ride firms like Uber threw tires across the road and set them alight.

The nationwide protest by licensed taxi drivers coincided with a walkout by air traffic controllers that forced airlines to cut flights by 20 percent, and another protest by teachers that disrupted schooling.

Prime Minister Manuel Valls told taxi driver representatives in a meeting that more efforts would be made to ensure other car ride services respected rules limiting them to pre-booked trips and returning to base after each one, according to a statement from the premier's office.

This measure would help to prevent them skimming off clients at airports and train stations from hail-down regular taxis, he told them.

Television footage from western Paris showed a number of protesters dropping tires from a higher byroad down onto the four-lane Paris ring-road, while others burned tires that blocked some lanes.

Police said they arrested around 20 people, most of them in western Paris. Valls warned in his statement that illegal acts would be pursued and punished.

The taxi drivers argue that the regulation of other car ride services is not being respected, leading to uneven competition at their expense from drivers and companies like Uber that do not have to pay as much to set up in business.

Uber has triggered similar protests by taxi drivers from London to New Delhi and led to legal disputes in a number of European countries.

The stoppages by air traffic controllers and teachers were part of a wider labor action by state employees, who are being urged by several unions to flex their muscles ahead of talks on long-running wage restraint measures.

About one in five flights to and from French airports were cancelled, according to the DGAC air transport authority. Schools had to contend with no-shows by teachers protesting against the reorganization of language learning and other aspects of secondary schooling, and also to demand that the government loosen a wage cap.

Civil Service Minister Marylise Lebranchu offered little prospect of a significant pay rise after five years of salary caps. Deficit reduction as well as spending rises on security after recent Islamist militant attacks have left the government little room for maneuver.

"The rate of economic growth and state receipts needs to be taken into account and I think that state employees are aware of that," Lebranchu told France 2 public TV.

French Protests and Strikes Disrupt Airports, Roads, Schools