PARIS (AFP) - The two leaders of Uber in France were taken into custody Monday as part of a probe into their ride-booking app which has sparked violent protests from regular taxi drivers, legal sources said.

The investigation was opened in 2014 into the application which is used to put paying clients in contact with cheaper, private drivers who do not face the same regulations as cabbies.

Uber has faced rising anger in several countries, particularly in France where a taxi strike last week turned violent as drivers set fire to vehicles and blocked highways, creating a headache for thousands of tourists.

The service has been illegal in France since January, but the law has proved difficult to enforce and it continues to operate.

Licensed cabbies say Uber is endangering their jobs by flooding the market with low-cost drivers.

San Francisco-based Uber, which offers several types of ride-sharing services, claims to have 400,000 UberPOP users in France.

However, its drivers do not pay the same level of social charges, do not need to undergo the 250 hours of training mandatory for French cabbies and do not require the same insurance as taxis.