Thousands of workers have gathered across France to protest against President Emmanuel Macron's plans to reduce retirement benefits, bringing the country to a standstill in the nation's biggest strike for a decade.

Workers from across the public transport sector, teachers, hospital staff and many others have taken to the streets to voice their opposition to plans to streamline the system that many fear will see them having to work longer and earn less after retirement.

People take to the streets in Paris in the mass walkout. Credit: AP

Crowds began gathering in large numbers on Thursday afternoon along the misty boulevards of Paris, many waving banners and singing.

Riot police were filmed dragging a protester along the ground as a cloud of smoke from tear gas and from what appeared to be flares billowed over demonstrators and officers.

Small groups of protesters smashed store windows, set fires and hurled flares in eastern Paris.

Some 6,000 police officers deployed around the city amid fears that yellow vest protest groups and extremist troublemakers could join the action.

Transport systems in Paris were largely brought to a standstill. Credit: AP

Authorities have issued a ban on protests on the Champs-Elysees, around the presidential palace, parliament and Notre Dame Cathedral.

As a precaution, all businesses, cafes and restaurants along the route have been ordered to close.

The walkout has also hit the city's tourist attractions, including the Eiffel Tower which remained closed on Thursday.

The Louvre Museum said it was open as usual but that some viewing rooms were closed.

Demonstrators in Paris. Credit: AP

The transport system was severely affected, with flights, trains and buses suffer cancellations, while most of the Paris subway system comes to a halt.

Nearly half of schools are closed.

Tourists cancelled travel plans to France in anticipation of the strikes, as police said it will deploy thousands of extra officers to help the country cope.

Easyjet, British Airways and Ryanair have also opted to cancel many of their flights to and from France.

A demonstrator walks on with raised fist in Bayonne, southwestern France. Credit: AP

Air France said around 30% of its domestic flights would be cancelled.

No tickets are available on Eurostar trains until Tuesday, with the company saying it had cancelled almost 100 services between now and then.

Workers at the national railway SNCF stopped work on Wednesday evening while other services planned to shut down on Thursday morning for an indefinite period.

Travel networks across the country have been hit hard by the strikes. Credit: AP

Hotels across Paris reported receiving numerous cancellations ahead of the strike, as wary tourists eyed closing transport routes and decided to skip their Paris trips.

The SNCF railway company expects nine out of 10 high-speed trains to be cancelled.

The French government said 55 per cent of teachers would be on strike on Thursday and hospitals will also be affected.

Unions across the country have taken part in the strike. Credit: AP

Why are workers striking in France?

France has dozens of different pensions schemes and Emmanuel Macron wants to create a single, unified system.

The move to a points-based system would reward employees for each day worked, but it would remove the most advantageous pensions for workers across a range of different sectors.

Unions fear that workers may have to work for longer for a lower pension.

France's current system is currently one of the most expensive in the developed world, costing the country 14% of its GDP. In comparison, the UK spends around 6%.