Large plumes of black smoke billowed over Sudan’s de facto wartime capital on Tuesday, as attacks on a city that had become a haven for civilians fleeing civil war stretched into a third day.

The Sudanese paramilitary group known as the Rapid Support Forces has launched a series of drone attacks on the military-controlled Red Sea city of Port Sudan, targeting key civilian facilities, including the airport and a hospital.

On Tuesday, drones hit a fuel depot near the port and the airport, according to multiple eyewitnesses, rattling the city and leaving its streets nearly deserted. Khalid Ali Aleisir, Sudan’s minister of information and the official government spokesman, accused the group, known as the R.S.F., of carrying out a “criminal and terrorist attack” in a post on social media.