A 27-year-old university student, Sarah was at a crowded fuel station in the city of el-Obeid, on the front line of Sudan’s civil war, when a drone struck without warning.

She says the station lit up before everything went dark. “In front of us there were injured people, blood, burnt cars, and smashed cars.”

We have withheld the student’s real name for her safety in a city that is the latest flash-point in the three-year war between the army and the paramilitary Rapid Support Forces (RSF).

Sarah told the BBC by phone that she was fortunate to survive the attack, but had sustained injuries.

“I got shrapnel in my leg and hand because I was outside the car when the second missile struck.”

Currently under army control, el-Obeid – the capital of North Kordofan state with a population of around 500,000 – has one of the largest military bases in central Sudan.

But the army has been unable to repel the drone strikes, with 27 hitting the city in June, the highest monthly total since the conflict began, according to violence monitoring group Acled.

UN human rights chief Volker Turk said at least 45 people were killed and 41 injured in 15 drone strikes between 6 and 28 June.

He added that the city has been under siege-like conditions for 18 months, with summary executions, abductions, torture and sexual violence taking place along routes used by people fleeing the conflict.

“The signs from el-Obeid are clear and unmistakable: Another human rights catastrophe is unfolding in Sudan,” Turk said last week in an address to the UN Human Rights Council in Geneva.

Nathaniel Raymond, the executive director of US-based Yale University’s Humanitarian Research Lab, told the BBC that el-Obeid was strategically significant for the warring sides, lying between the RSF-controlled west of the country, with the east mostly in the hands of the army.

“If you control el-Obeid, you control the road to the capital, Khartoum and [its twin city] Omdurman, and so the army has to defend el-Obeid,” he said.