In France, air traffic controllers went on a walkout and taxi drivers disrupted traffic by burning tires on Tuesday in protest against labor conditions.

The so-called Black Tuesday of strikes saw the two groups joining civil servants, hospital workers and teachers in the protest action.

According to Paris police, 20 people were detained in connection with the strikes.

Taxi drivers lit bonfires on a major highway leading to the capital, Paris. One in five flights was also canceled in the city, while other flights faced delays.

Local television reported that two people were injured at Orly Airport when a shuttle bus tried to force its way past a blockade by taxi drivers.

Traditional taxi drivers say they are suffering unfair competition from the US-based transport company, Uber.

Dozens of the taxi drivers tried to march onto an eight-lane bypass, but police pushed them back with tear gas.

Teachers are also on strike over wages, education reforms and unfair working conditions.

The protests are the latest in a string of challenges to the administration of President Francois Hollande amid low economic growth and a record-high unemployment rate.

Prime Minister Manuel Valls met with taxi drivers in an apparent attempt to defuse tensions.

Uber has faced legal challenges from governments all around Europe. Its lowest-cost service is banned in France and two Uber executives go on trial next month in Paris for fraud.

Karim Asnoun, head of the CGT Taxi Union, said at Tuesday’s Paris protest, “Unfortunately the governments are weak and as unemployment is pressuring them, they cede. They think they are creating jobs, whereas for every created job there is one that's destroyed.”

Elsewhere, Rachid Boudjema, the president of the taxi drivers union in Marseille said Uber is targeting “professionals who are paying taxes, who respect the rules.”

“American cowboys …. want to destroy our system, the system we are all attached to.”

Uber, meantime, sent a message to its French customers warning of potential violence, saying the goal of the Tuesday protest action is “to put pressure on the government to ... limit competition.”