Uber is launching its service in Argentina's capital city in defiance of local authorities and despite protests by local cab operators.

The company says more than 10,000 of its drivers are available in Buenos Aires as of Tuesday afternoon.

Uber says it will be successful because its prices are below tariffs regularly charged by local taxi drivers. It also says thousands of residents of Buenos Aires have already downloaded the ride-sharing app.

The Buenos Aires mayor's office has warned that Uber is not authorized to operate yet because it doesn't meet requirements for transporting passengers.

Local cabbies blocked several streets and avenues to protest, saying the service puts their livelihood at risk.

Uber drivers have previously faced angry protests in Mexico City, Paris and other cities.