French workers demonstrate in Marseille on Tuesday against government plans for pension changes. (Jean-Paul Pelissier/Reuters)

Commuters in France and London faced major delays on public transit Tuesday morning as workers in both countries staged 24-hour strikes.

In France, unions launched the strike to protest a government plan to change the pension system, including a proposal to raise the minimum retirement age from 60 to 62.

Meanwhile, commuters in London dealt with rush-hour chaos after London Underground workers took part in a one-day strike, closing much of the city's busy subway system.

Many rush-hour trains were cancelled in the Paris region, and people with medium- or short-haul flights faced long delays and cancellations because of disruptions to air-traffic control services.

Schools and hospitals will also be affected by the strike, union leaders say.

Nearly 200 rallies are planned around the country, and union officials hope as many as two million people will participate. A similar effort June 24 drew nearly 800,000 people.

The French strike coincides with the start of debate in parliament over a plan to overhaul the money-losing pension system so it will break even in 2018.

Private and public sector workers demonstrate over pension reforms in Marseille on Tuesday. (Jean-Paul Pelissier/Reuters)

"If the government wants the next step to go well, it has to give a serious response to the proposals that we ourselves have made," said Francois Chereque, who heads the moderate CFDT union.

Chereque told the RTL radio station he wants Tuesday's protests to "restore hope" for citizens while putting pressure on the parliamentary debate.

The government has said the changes are needed to deal with an aging population and huge national debt. Labour Minister Eric Woerth has said the government will press ahead with the retirement changes no matter how strong the protest turnout is.

The French retirement age of 60 is already among the lowest in Europe. In contrast, neighbouring Germany has decided to bump up the retirement age from 65 to 67 and the U.S. Social Security system is gradually raising the retirement age to 67 as well.

Strike slows London Underground

Across the English Channel, much of the London Underground was shut down to protest the planned layoffs of roughly 800 ticket takers.

"The sidewalks in general are buzzing, the buses are jam-packed," Thomas Ledwell of CBC News said from London. "Even the roads are much more congested than they usually are at this time of day."

Thousands of workers walked off the job Monday evening because of a dispute over the cuts, which workers say will hit safety and service.

Limited services are operating, but the strike disrupted the morning commute for millions of rush-hour passengers, the BBC reported.

This is the first of a series of 24-hour strikes planned by London Underground workers in response to staffing cuts.

The London Chamber of Commerce estimates that every day the underground is closed will cost the city's economy roughly $76 million.

With files from The Associated Press