Some Uber Technologies drivers in South Africa have gone on strike as the cost of running cars increases with higher fuel prices.

Drivers at the US ride-hailing service gathered peacefully at a public park in central Johannesburg on Monday to discuss their grievances and aren’t available for trips, an Uber spokesman confirmed by phone. They’re unhappy about the 25% service fee charged by Uber per ride, especially after the government hiked fuel prices for the third time this year.

“We are aware of a small group of driver-partners who are planning on going offline or will not be using the app today,” Alon Lits, head of sub-Saharan Africa operations, said in an e-mailed response to questions. “The 25% service fee is designed in a way to ensure that the business is sustainable for both Uber and our driver-partners.”

The arrival of Uber in South African cities from 2013 has sparked several, often violent, protests by drivers of traditional taxis, but those operating Uber vehicles have mainly gone about their business.

Defending the fare structure, Lits said that “in cities across the world lower fares mean greater demand, lower pickup times and more trips per hour”. — Reported by Ntando Thukwana and Loni Prinsloo, (c) 2018 Bloomberg LP