Taxi drivers and Colombian users of Uber are butting heads over a government ban on the ride-sharing company.

Amid threats of a strike by yellow taxis, the Transportation Ministry this week declared illegal all smartphone applications that facilitate the hiring of cabs that aren't registered for that purpose.

Taxi drivers around the world fearing a loss of business from Uber's credit card-only, spruced-up service have challenged the Delaware-based company on similar grounds.

The service has won an especially loyal following in Colombia since arriving earlier this year. The reason is simple: a fear of being ripped off or even assaulted by taxi drivers with a reputation for violence.

A spokeswoman for Uber on Wednesday said the company hadn't been notified of the ban and continues to operate normally.