Violent clashes between protesters and police have also broken out in the French city of Nantes. Nationwide protests have disrupted several sectors across France, with air travel among the worst affected.
One demonstrator and five officers were injured in violent clashes between French riot police and opponents of a controversial new labor reform bill in Paris on Thursday.
Demonstrators threw Molotov cocktails at police, who responded by firing teargas and launching stun grenades. One officer is believed to have sustained burn injuries. At least a further 15 people were arrested.
Violent clashes were also reported at a demonstration in the western city of Nantes, where police resorted to firing tear gas and water cannons at the protesters.
Thursday's clashes are the latest in a number of demonstrations against proposed employment law reforms. Around 13,000 people took part in the Paris rally, the 14th such protest in just six months.
Police estimated that around 78,000 people took part in the demonstrations nationwide. Organizers estimate the total turnout to be around 170,000.
Both estimates are lower than at the start of the rallies six months ago, when hundreds of thousands took to the streets. Violence at the rallies peaked just four days after the Euro 2016 football championships, where around 40 people were injured and dozens arrested.
Away from the sporadic moments of violence, thousands of union activists marched peacefully through Paris. Philippe Martinez, leader of the CGT union, said he was committed to continue fighting the new law in the country's courts and at the individual company level. Workers, he said, should continue "fighting tooth and nail to stop [the law]. "
French industry disrupted
Nationwide protests upset many major French industries on Thursday.
A focal point of the protest was in the eastern city of Belfort. The major train-building company Alstom is currently locked in battle with the French government over the closure of a locomotive factory.
Alstom announced that would close the plant and move production 200 kilometers (120 miles) north.
The city is intertwined with the locomotive and train industry. The Belfort factory produced the first steam train in the late 19th century and has gone on to assemble France's high-speed TGV trains.
Hundreds of workers and demonstrators marched through the streets, chanting "Alstom is Belfort, Belfort is Alstom."
Numerous flights in and out of France were canceled as air traffic controllers across the country went on strike. Airlines had been advised by aviation authorities that they would need to cancel 15 percent of flights into Paris airports.
Hollande's labor reform bill
Union leaders are seeking to quash the Socialist government's plans to adopt more liberal labor laws that would grant employers more freedom to extend the work week and fire staff. French President Francois Hollande said making the country's famously rigid employment laws more flexible would encourage hiring and investment. He has said he anticipates a 10 percent drop in unemployment on the back of these laws.
Unions have said the new laws signal a major blow to hard-won workers rights and bargaining power. Conservative critics, meanwhile, deem the laws insufficient in providing a much needed jump start to the French economy.
Left-wing opposition to the bill was so great that the government forced it through by decree, causing major divisions and ruptures within the Socialist Party.
dm/sms (AFP, dpa, AP)