Just a few days after Uber launched its service in Portland, Oregon, the city has filed a lawsuit against the ride-sharing startup for operating without required permits, and has also issued the company a cease and desist order.

This comes after the Portland Bureau of Transportation warned Uber to be ready for civil and criminal penalties. Like other similar cases, city officials claim to be concerned about the way Uber handles insurance and background checks of its drivers.

The Transportation Bureau already issued a couple of civil penalties to Uber yesterday, one for operating without a company permit and another for operating without a vehicle permit.

"I am hereby directing that Uber Technologies Inc.... or any other Uber affiliate entity immediately cease and desist operating within the City of Portland until such time as appropriate permits are obtained and Uber is in full compliance with the requirements of Portland City Code Chapter 16.40," said Transportation Director Leah Treat. "Please alert all Uber-affiliated drivers that they are to cease and desist."

As per the rules, it is illegal for motorists to pick up passengers for a fee in the Portland city limits without proper permits. Although taxis that pick up passengers outside of Portland may drop off those passengers in the city without a permit, they can't ride with a paid passenger on the way back.

Meanwhile, Uber has said that the company has received a "tremendously warm" welcome from riders and drivers in and around the city, and is claiming that over 8,000 Portland residents have signed an online petition in its support.