Protesters in France have clashed with police against a divisive labour reform bill that they say is too "pro-business" and makes it easier for companies to fire staff.

At least 40 people were injured and 73 arrested on Tuesday as some 75,000 demonstrators amassed in Paris in the latest round of protests against the controversial reforms.

According to police, 29 members of the security forces were among the 40 injured.

The AFP news agency reported that hundreds of masked protesters hurled objects at police and stormed a building site in the capital.

Sparking months of street protests and widespread opposition, the bill, which was pushed through last month, retains France's cherished 35-hour working week but allows companies to organise alternative working times.

Those include a working week of up to 48 hours and 12-hour days for temporary periods. In "exceptional circumstances", employees could work up to 60 hours a week.

Strikes on Tuesday also closed the Eiffel Tower and disrupted transport links as tens of thousands of fans continue to pour into the country for the Euro 2016 football event.

Al Jazeera's Mohammed Jamjoom, reporting from Paris, said the protest was rambunctious but peaceful and only flared up when demonstrators arrived in the area of Les Invalides.

"When police brought in water cannon trucks and fired tear gas to disperse the crowds - that's when the clashes intensified," our correspondent said.

"Most of the people we spoke to said they didn't want the protest to turn violent. They believed that would detract attention from the demonstration which was essentially demanding that the government revoke these labour reforms."

"Many of the protesters were saying that the reforms in and of themselves were bad enough, but the fact that these were being pushed by a socialist government - made it worse. They were saying a socialist government should protect the workers not the employers," he added.

The strike is the latest in months of industrial action that has seen air and rail transport severely disrupted, fuel shortages and rubbish piled up on the streets of Paris.

France's Senate started debating the reforms on Monday, which are aimed at making the job market more flexible and reducing high unemployment - but critics see the reforms as too pro-business.

Protests against the reform started on March 9, culminating in massive demonstrations on March 31 that brought nearly 400,000 people on to the streets.

Labour Minister Myriam El Khomri, restated the government's strategy before the protest, saying that the law could be tweaked in detail but there was no question of gutting it of the essentials or of dropping it.

France's deeply unpopular President Francois Hollande has just over a year left in office and had been banking on the labour reform as a standout initiative with which to defend his record.