Taxi drivers in France are blockading roads with burning tires in protest at the low-cost Uber app, resulting in at least 20 arrests. Air traffic controllers are also staging a demonstration, leading to dozens of canceled flights.

At least 20 arrests had already been made by 10 a.m. local time, following taxi driver protests around major cities including Paris and Marseille.

Drivers blocked roads with burning tires, prompting the arrival of riot police and firefighters. Some drivers had set pre-dawn bonfires which authorities had to put out.

Des pneus brûlent sur le périphérique #PorteMaillotpic.twitter.com/CfMyOKhyJQ — Paul Louis (@paul_louis11) January 26, 2016

Hundreds of taxis, joined by a few from Belgium and Spain, blocked a massive intersection leading into western Paris, causing huge disruption to the area.

Dozens of drivers tried to march from Porte Maillot intersection on to an eight-lane road, but police pushed the back with tear gas.

Drivers also staged ‘go slows’ on roads, causing major traffic jams.

One taxi driver was injured when a shuttle bus at Orly Airport forced its way through a blockade. Other drivers then threw stones at the windows, forcing passengers to get off the bus and walk.

The protesters threw firecrackers in front of the Palais des Congrès de Paris at Porte Maillot.

Activists from the taxi drivers’ trade union shouted slogans such as “Left to die economically, will die at Porte Maillot.”

Des pétards sont lancés devant le Palais des Congrès. Des bombes agricoles se font également entendre #grevetaxispic.twitter.com/ehylLM9abm — Malik Acher (@malik_acher) January 26, 2016

Prime Minister Manuel Valls has condemned the “unacceptable” violence during the protests.

"There is a right to protest... even during a state of emergency," he said on Tuesday. "But violence is unacceptable."

Following a meeting with representatives of taxi drivers’ organizations in Magtignon on Tuesday, Valls announced that a government mediator will be appointed to resolve the economic crisis that has hit the sector.

There were also blockades around Charles de Gaulle Airport.

Meanwhile, protesters in Paris at Porte Maillot have expressed their intentions to stay all night, according to RT France correspondent Malik Acher.

Un manifestant fait part de la détermination des Taxis à rester à la Porte Maillot #grevetaxispic.twitter.com/cYsBB0mVmc — Malik Acher (@malik_acher) January 26, 2016

#greve26janvier my personal favorite: a makeshift kitchen with mint tea pic.twitter.com/zEqicjPv9c — Anna Baranova (@AnyaFedorova_RT) January 26, 2016

The taxi drivers are protesting over working conditions and competition from non-traditional services such as Uber.

Uber drivers "vandalize professionals who are paying taxes, who respect the rules," Rachid Boudjema, president of the taxi drivers union in Marseille, told AP.

In response to the protests, Uber sent a message to its French customers which said that the goal of the demonstrations was “to put pressure on the government to...limit competition.”

Meanwhile, a planned walkout from air traffic controllers prompted the French civil aviation authority, DGAC, to call on airlines to cancel one in five flights.

EasyJet said it had cancelled 35 flights, although Air France said it would operate more than 80 percent of its short and medium-haul flights in France and Europe. It did, however, stress that “last-minute delays or cancellations cannot be ruled out."

Social networks users denounced violence at the protests. Some people even urged a boycott of traditional taxis and to use Uber instead.

Je comprends votre colére mais ça justifie pas la violence pour autant. #Taxis — TNB (@TheBoySabb) January 26, 2016

"les #taxis ce sont des connards, vive @UberFR !!" hm pourquoi pas mais ils ont redescendu leurs prix depuis le 13 novembre au moins? — Alex 3 Tears (@HelloImAleex) January 26, 2016

Hundreds of thousands of civil servants and teachers also went on strike on Tuesday, protesting against a pay freeze and poor salaries. Teachers are scheduled to march in cities across the country on Tuesday afternoon.

It's the newest challenge to Francois Hollande's Socialist government and its stop/start efforts to modernize the economy, in response to low economic growth and record-high unemployment. Earlier this month, Hollande announced what he called a “state of economic and social emergency,” involving a €2 billion (US$2.1 billion) plan to revive hiring and catch up with the world’s economy.

Incendies et détonations sur l'A25 près de la métropole européenne de Lille. CRS prêts à charger. #LTmanifestationpic.twitter.com/rtEcAUhMgn — Gabriel Dewallens (@DewallensGaby) January 26, 2016

The protests come just one day after French farmers demonstrated against the prices of dairy and meat products in the province of Brittany, blocking roads and burning tires. The farmers demanded that prices be increased because the proceeds from their sale don't cover the cost of production.