Hundreds of taxis on Thursday drove at a snail's pace across the Polish capital Warsaw in protest at the ride-sharing app Uber and other unlicenced competitors.
Other cab drivers gathered in front of the justice ministry to call for legislation to regulate the industry.
Traditional cab operators argue that the Uber app and others like it represent unfair competition because their drivers can dodge the rules and restrictions that regulate professionals.
"There are 12,500 legal taxis in Warsaw and around 8,000 to 9,000 unregistered working for Uber, Taxify and a couple dozen other similar app-based operators," said Jaroslaw Iglikowski, head of the Warsaw Taxi Drivers union.
"The app-based operators are taking around 30-35 percent of our overall business and up to 70 percent of night-time fares, especially on weekends," he told AFP.
The protesting cab drivers claim in a petition they gave the justice minister that the country is losing more than 700 million zloty (160 million euros, $190 million) annually in unpaid taxes because of Uber and others like it.
The taxis dispersed in the early afternoon before rush hour, as the drivers had promised they would not cause traffic problems for city residents.
Uber has become one of Silicon Valley's biggest venture-funded startups and has expanded its ride-sharing services to dozens of countries.
It does not employ drivers or own vehicles, but instead relies on private contractors using their own cars, allowing them to run their own business.
The app claims it is a service provider, connecting passengers with these freelance drivers directly and cheaply.
But critics and competitors around the globe say this allows it to flout costly regulations such as stringent licensing requirements for taxi drivers, who undergo hundreds of hours of training.