Several hundred youths clashed briefly with police in Paris at the end of a huge union rally called to denounce the French government's handling of the economic crisis.
Some 500-600 youths set fire to rubbish bins, smashed phone booths and threw bottles at the security forces.
Police fired teargas to disperse the crowd, swiftly leaving the huge Nation square in eastern Paris, which was the focal point of today's union rally.
French media reported outbreaks of violence in at least two other cities during the day but said police swiftly brought the troubles under control.
Up to 3m people took to the streets across France to protest against President Nicolas Sarkozy's response the economic crisis and demand more help for struggling workers.
Similar violence marred a first day of union action on 29 January and such confrontations between protesters and police are relatively common at French demonstrations.
The action has caused the cancellation of one in three flights out of Paris' second airport, Orly, though civil aviation officials said 90% of flights were running out of the main Charles de Gaulle airport.
The state rail operator SNCF cancelled 40% of the high-speed intercity TGV services and half of other regional trains.
Commuters heading into Paris were spared major disruption due to a new law enforcing a minimum service during strikes, while Metro and bus lines were running normally.
But with up to half of primary teachers on strike, many parents stayed home from work to look after their children.
According to a poll published this week, 78% of French people believe the one-day action is justified.
The protest comes at a time when several unrelated disputes have surfaced around France.
The government is anxious to prevent the separate strands of discontent from melding into one major protest movement that could paralyse the country.
Mass layoff plans
Companies across France have announced mass layoff plans and in some cases staff have responded with shock tactics.
Workers hurled eggs at managers last week to protest against the closure of their tyre plant by German group Continental that will eliminate 1,120 jobs.
Workers held managers hostage at a Sony plant for a night last week to demand more redundancy money when their factory closes in April, destroying 311 jobs.
Oil giant Total caused national outrage last week when it announced it would shed 555 jobs, days after unveiling record profits for 2008.
Junior Employment Minister Laurent Wauquiez said this was 'scandalous'. Total employees have staged strikes.
Students and lecturers have launched a series of strikes, sit-ins, sieges and boycotts for several months to protest against two separate government reforms.
The disputed reforms would give university rectors new powers to decide how much time lecturers spend teaching as against doing research, and would scrap dedicated teacher training colleges in favour of extra classes at university.
The government has agreed to review its plans, but unrest has continued unabated and many universities have been in chaos for weeks.
School teachers and pupils have been campaigning since early 2008 against government plans to shed jobs by not replacing retiring teachers.
It already cut 11,200 jobs in education that way at the start of this academic year and plans to reduce payroll by a further 13,500 by the next academic year. There have been countless strikes and demonstrations.
A government plan to reform the way hospitals are run and to shut down small hospitals to create bigger hubs in large towns has caused anger, strikes and demonstrations.
Youth gangs in several poor suburbs around Paris have staged violent attacks in recent weeks that have caught the public imagination.
In one case, in the town of Gagny, a gang invaded a school and attacked pupils using metal bars and hammers. 12 people were injured and more than a dozen were arrested.
President Nicolas Sarkozy demanded that the government work on an emergency plan to curb gang violence.