The torching of two vehicles used by Uber drivers in Johannesburg Thursday night has South Africans alarmed over another escalation in months-long tensions between traditional taxi drivers and their less expensive competition.

Witnesses said they watched as armed men accosted the two Uber cars at a commuting spot in the Sandton neighborhood, forcing their occupants out of the vehicle at gunpoint. Minutes later, the vehicles were engulfed in flames after the attackers poured an accelerant and set them on fire.

Police used rubber bullets and stun grenades to disperse a crowd of about 50 people engaged in a melee that followed the attack.

“We’re aware of the situation in Sandton. At this time we can confirm that one vehicle is registered to use the Uber app,” said Uber South Africa. “We are currently investigating the second vehicle.”

Both drivers appeared to have escaped serious injury, although one was too shaken to speak with local media. A different Uber driver described what happened and said the attackers were taxi drivers, who have become increasingly violent as they see Uber service become more popular and cut into profits.

The Gauteng Meter Taxi Council has for months demanded that Uber drivers be licensed and subject to the same rules they are in order to establish more fair competition.

This most recent incident occurred near a Gautrain station already on a list of locations identified as dangerous “no go” zones for Uber drivers, and is the latest in a series of attacks that have left Uber drivers dead or seriously injured. In July, a driver in Pretoria died from severe burns after his vehicle was torched. Last month, acid was thrown in the face of another Uber driver in Johannesburg.