Violence mars Paris police protest
Police in 60 French cities have taken part in rallies to demonstrate against what they call a rise in anti-police violence - only to be met with a fierce counter-protest in Paris.
Police say there has been an escalation of violence in protests against labour reforms over the past two months.
As officers protested in Paris, they were targeted by counter-demonstrators.
Groups say police have themselves acted violently towards them.
As hundreds of police gathered for a rally at the Place de la Republique in Paris on Wednesday, hundreds of the counter-demonstrators defied a ban on marching.
While some chanted "Everybody hates the police" and "Police everywhere, justice nowhere," French media said up to 15 youths attacked a police car with iron bars before throwing a petrol bomb at the vehicle.
Two police officers who were inside the car fled before it was attacked, media said.
Paris prosecutors say they have opened an investigation into attempted manslaughter.
French Interior Minister Bernard Cazeneuve said 350 police officers had been injured over the past two months. The violence has been blamed on small groups of "casseurs", or troublemakers.
"Anti-cop hatred comes from a small portion of the population," Jean-Marc Falcone, general director of the police, told Europe 1 radio. "But these 10% are very violent."
"Since the first demonstration on 9 March, we notice that they [the police] generate the violence," one labour reform protester, Vanina Giudicelli, told the Associated Press. "We have been sprayed by gas, hit with batons, arrested."
She called the police demonstration "a real provocation".
France's Socialist government pushed through the labour reforms last week, saying they are essential to help cut high levels of unemployment.
The changes to the labour laws make it easier for employers to hire and fire, but opponents fear they will also enable employers to bypass workers' rights on pay, overtime and breaks.