Egyptian security forces fired tear gas Tuesday to disperse taxi drivers who had blocked a major road in the capital, Cairo, to protest Uber and other car-hailing applications, which the head of the Cairo traffic police insists are illegal.

The drivers stood in a roundabout on Gameat el-Dowal street after the canister was fired at them when they left their cars, witness Lamia el-Etriby and taxi drivers at the protest said. They had blocked all but one lane, causing a major traffic jam as police vehicles arrived on the scene.

"We are not leaving until an official comes and gives us his word that all these apps will be shut down in Egypt," said Sherif Ali, a taxi driver and one of the protest organizers.

Taxi drivers have been protesting Uber's presence in the country in recent weeks. The application has very rapidly become popular in Cairo, a city of 20 million people with almost-constant traffic jams.

Taxi drivers have complained that Uber drivers have an unfair advantage because they do not have to pay the same kind of taxes or fees, nor follow the same licensing procedures. Now the Egyptian government appears to be agreeing, and launching a crackdown on the service.

Maj. Gen. Alaa el-Degwy, the head of Cairo's traffic police insists Uber and a similar app named Careem are Illegal as taxis require different processes and rules. He said police in Cairo have begun clamping down on Uber drivers at checkpoints, and those who are caught must pay a fine. The police also cancel the driver's license, take the car license, and refer the driver to public prosecutors, he said.

In addition to paying specified taxes, drivers must carry a special license and be registered as a taxi, said el-Degwy, who added that officers have even brought disgruntled taxi drivers along to demonstrate the crackdown in action.

Egyptian clients say they prefer the dependability of the app, complaining that normal taxi drivers often tamper with their meters or pretend the meter is broken in order to overcharge them. They also appreciate the safety provided by the app, especially for female passengers at night who fear being sexually harassed by drivers in a country where sexual harassment is endemic. Uber says it trains all drivers who enroll with the service, with particular emphasis on eliminating sexual harassment.

"As a victim of multiple sexual harassment incidents in cabs and by other drivers, Uber really made my life as a woman safer and easier in Cairo," said 31-year-old Radwa Al Rifai, adding that she is "shocked" at the government's measures "to take away from us the one safe means of transportation."

David Plouffe, Uber's chief adviser and a member of the board of directors, is currently visiting Cairo. He told The Associated Press that the service has boomed in Egypt as both passengers and drivers embrace it. As many as 10,000 drivers have enrolled with Uber, including 600 who started on Monday alone, he said.

"They are taking some of our livelihood and splitting it with us," said taxi driver and protester Yasser el-Sharqawi. "We get fewer clients and when we get them they tell us, 'We will be using Uber and Careem instead.'"

In addition to the police crackdown, Uber drivers have faced vigilante violence from taxi drivers. In some instances, Uber drivers have responded to an order and found an angry mob of taxi drivers waiting to drag them to a police station.

Uber Egypt General Manager Anthony el-Khoury said that he and Plouffe, the visiting board member, plan to meet with government officials this week to find solutions to this standoff and ways to coexist.

"There is still discussion that will happen between us and the government to see if they feel comfortable with these types of regulations, or we can work toward stronger regulations so that we can coexist in a more transparent way," said el-Khoury. "I think there's a misconception that this is a zero sum game."

El-Khoury said that Uber has brought some "healthy competition" that might be pushing taxi drivers to address their customer-service issues. Protest organizer Ali said that drivers have begun organizing training courses against sexual harassment and thinking about ways to improve their services.

El-Khoury told AP that Uber drivers do pay Egyptian taxes through an indirect route. The company only hires drivers who are licensed through private limousine or car rental companies, which do pay their own corporate taxes, he said.

"This is a circumvention of the law," said el-Degwy, of the Cairo traffic police. "You cannot have a citizen riding in a car with someone he knows nothing about."