Witnesses reported air, tank, and artillery strikes shook Sudan’s capital, Khartoum, and the neighboring city of Bahri on Friday, mocking a 72-hour truce extension promised by the army and a rival paramilitary organization.

Hundreds of people have been slain and tens of thousands have fled for their safety as a power struggle between the army and Rapid Support Forces (RSF) erupted on April 15 and paralyzed an internationally supported transition to democratic elections.

The fighting has also reawakened a two-decade-old conflict in the western Darfur region where scores have died this week.

In the Khartoum area, heavy gunfire and detonations rattled residential neighborhoods. Plumes of smoke rose above Bahri.

“We hear the sounds of planes and explosions. We don’t know when this hell will end,” said Bahri resident Mahasin al-Awad, 65. “We’re in a constant state of fear.”

The army has been deploying jets or drones on RSF forces in neighborhoods across the capital. Many residents are pinned down by urban warfare with scant food, fuel, water and power.

At least 512 people have been killed and close to 4,200 wounded, according to the United Nations, which believes the real toll is much higher. The Sudan Doctors Union said at least 387 civilians had been killed.

The RSF accused the army of violating an internationally brokered ceasefire with air strikes on its bases in Omdurman, Khartoum’s sister city at the confluence of the Blue and White Nile rivers, and Mount Awliya.

The army blamed the RSF for violations.

The ceasefire is supposed to last until Sunday at midnight.

The violence has sent tens of thousands of refugees across Sudan’s borders and threatens to compound instability across a volatile swathe of Africa between the Sahel and the Red Sea.

“From the war planes to the tanks and rockets, we had no other option than to leave,” said Sudanese man Motaz Ahmed, who arrived in Egypt’s capital Cairo after a five-day trip. “We left behind our homes, our work, our belongings, our vehicles, everything, so we can take our children and parents to safety.”

Foreign governments airlifted diplomats and citizens to safety over the past week. Britain said its evacuations would end on Saturday as demand for spots on planes had declined.

The U.S. said several hundred Americans had departed Sudan by land, sea or air. A convoy of buses carrying 300 Americans left Khartoum late on Friday on a 525-mile trip to the Red Sea in the first U.S.-organized evacuation effort for citizens, the New York Times reported.