Scores of civilians have been killed and hundreds injured, according to a doctors' union. These scenes are from Khartoum International Airport.

"Go fast, go fast!"

And on the streets of the city, civilians are describing scenes of chaos as they struggle to source even basic necessities such as water, or medicine. The U.N. World Food Programme says it's been forced to halt operations in several areas and three employees were killed.

This is an Indian travel blogger, Maheen S.

"Me and my friend trapped in the road because army has started taking over many roads ahead and they are checking all the vehicles. When we tried to cross to our place, they started raising the gun, then we ran away. See, army's there."

"All the water, all milk, everything is empty here on the refrigerator. See, everything is khalas (finished), nothing left, food stock is not available."

RSF soldiers seen here. They're saying God is the greatest, and that they've destroyed the Sudanese army at the airport - who they call "mercenaries," including its leaders.

Both sides say they've made gains against the other. Reuters has verified video showing them in some locations, but can't verify claims of their successes.

The RSF is a former militia that was due to merge with the army and whose leaders shared power ruling the country in a military council. Both were due to release their power as the country transitioned toward a civilian democracy.

Friction over the integration brewed for months, but it's not clear who shot first. The RSF says the army tried to seize full control in a plot. The army accuses the RSF of mobilizing its forces, illegally, and moving on strategic sites.

The future of Sudan's democracy is, once again, uncertain.