The controversy over online cab service Uber has taken a violent turn in Mexico City, where traditional taxi drivers – worried that their business will become extinct – have threatened and attacked these freelance drivers and even smashed up their cars in the hope of driving them off their turf.

Uber, which lets practically anyone with a car work as a driver, and its competitor Cabify have become the bane of Mexico City's taxi drivers, who operate the largest fleet in the world, with 140,000 registered cabs. Their distress has boiled over from run-of-the-mill protests to full-out attacks and threats of even more retribution.

"We are not going to leave (Uber cars) alone. We are tracking these colleagues and hunting them down," Esteban Meza, a leader of one of the city's taxi unions, told El Universal. "Without doubt this is going to generate big trouble," he added.

While disputes over Uber, a billion-dollar global business, have arisen in cities as far flung as Chicago, Berlin and Manila, Mexico City's already factional cab services have taken the furor to a new level as established taxi drivers complain that the "pirate" cabs are skirting rules and dodging payments for permits and other tariffs.

Licensed cabs in Mexico City have to pay expensive rates for their permits, which Uber drivers don't have to. The city transport authorities also make licensed cab drivers to take courses, paint their cars in a uniform recognizable color (currently pink), all which, cabbies say, cuts into the low overhead they make during their sometimes 14-hour shifts.

Uber is particularly popular in the city's upscale and trendy neighborhoods, where app users can pay in plastic and be less scared of random muggings than if they were in a regular cab. This had led to complaints from traditional cab drivers that Uber drivers are using their designated stands and causing business fall by about 40 percent this year.

"We can't compete against this illegal company," Jesus Juárez Cruz, 34, a driver and representative of a taxi stand in the wealthy Bosques de las Lomas neighborhood told the Washington Post. "For so long, we've been paying the government our taxes, and it's not fair that overnight they give everything to a company that breaks the rules."

With their business interests threatened, many Mexico City taxi drivers have decided to take a low-tech approach to combating their high-tech counterparts: baseball bats to the windshields of Uber cars, smashed taillights, slashed tires and bareknuckle brawls.

The threats and violence directed toward Uber drivers have forced many of the freelance cabbies to keep a low profile – keep their phones below their windshield, telling police they are private chauffeurs and avoiding hotspots where taxi drivers have attacked before.

"The taxi drivers can be really aggressive. They can block you in and break your mirrors and scratch the car. They attacked a colleague by a taxi stand. They smashed all his windows and beat him," Uber driver David García told Time Magazine.

Still, García said the protests of the cab drivers – and even the violence – aren't going to deter him from the lucrative opportunities of driving an Uber car. He says he now earns 2,300 pesos – or $150 – a week driving an Uber, more than he did in a previous job working on a stall.

Also, the complaints and media coverage that the taxi drivers are generating, Garcia says, is only helping business for Uber.

"It is fine the taxi drivers speak out," he added. "They are just giving us publicity."