A national train strike was launched by French trade unions on Wednesday in protest against a proposed railway reform aimed at containing the sector's soaring debt, the Associated Press reported.

Although the 24-hour strike began on Tuesday evening, French commuters will face traffic woes on Wednesday when train links to other countries are also hit, according to the SNCF state rail body.

With regional trains also being affected in the busy Paris region, only one high-speed TGV out of two or three will be operating.

While three out of four Brussels- and Amsterdam-bound Thalys trains will be operational, Eurostar trains to and from London will run on their normal schedule.

According to the AP, trains to Germany will be unaffected, but those going to Spain will be disrupted.

"The number of strikers will be high, notably among ticket collectors and drivers," more than half of whom have said they are prepared to observe the strike, said SNCF human resources director Francois Nogue.

Passengers were advised by the state rail to put off their travel if possible, and for those travelling in by road to consider car-pooling.

Traffic was already noticeably heavier than normal on the streets of Paris late Tuesday.

"The strike takes place just one week before France's lower house examines the proposed railway reforms aiming to tackle the sector's soaring debt," the AP reported.

"Transport minister Frederic Cuvillier said Tuesday the railway sector's debt currently stood at more than 40 billion euros ($54 billion), and would likely soar to 80 billion euros by 2025 if nothing was done to stem it."

"The problems for commuters in the French capital Wednesday are exacerbated by a protest by taxi drivers in several European capitals, including Paris, against what they see as unfair and illegal competition from app-using car services such as Uber which have shaken up the taxi industry."