By Jim Melwert

PHILADELPHIA (CBS) — A popular on-demand taxi service hit the streets of Philadelphia this weekend, but without the blessing of the Philadelphia Parking Authority, which regulates taxicabs and limousines in the city.

That sparked a war of words on social media, and a half-dozen citations to drivers.

Today, the mayor was weighing in as well.

Uber’s lower-cost service, UberX, debuted in Philadelphia, offering free rides for its first weekend here.

But, since it’s unlicensed in the city, the Parking Authority cracked down.

“Over the weekend there were six cars impounded, six drivers fined $1,000 each, and Uber was also fined $1,000 for each vehicle,” says Vince Fenerty, executive director of the Parking Authority.

Fenerty says they’ll continue that crackdown.  He notes that UberX is prohibited from operating in the city because vehicles aren’t inspected, drivers don’t have the proper license, and he questions their insurance coverage.

Uber spokesman Taylor Bennett disputes the safety and insurance, saying they’ll continue their service and will back their drivers.

“We’re going to support them 100 percent and cover the costs of any financial or legal fees associated with those citations,” Bennett says.

Today, mayor Michael Nutter was also weighing in, saying Uber needs to operate legally but, as he put it, the Parking Authority is “blocking” them.  He wonders whether the PPA’s recent (and unsuccessful) efforts to  sell taxi medallions for more than $400,000 each has something to do with its decision.

“Maybe because there’s a potential conflict there for the Parking Authority, given that they’re heavily invested and very active with the cab industry, they may not want that kind of competition here in Philadelphia,” the mayor said.

Nutter said people looking for transportation deserve as many options as possible, and he wants to see both sides sit down and figure it out.

The Parking Authority issued a statement in response saying that it is not taking a stand for or against Internet-based ride services such as Uber, but was simply enforcing the law as it currently stands.