Air strikes by the army targeting the paramilitary Rapid Support Forces (RSF) were heard across several residential neighborhoods in southern Khartoum, including near the Taiba camp, while a police reserve force aligned with the army battled the RSF on the ground, the witnesses said.
"The bombardment and the clashes don't stop and there's no way to flee from our homes. All our money is gone," said Salah el-Din Othman, a 35-year-old resident of Khartoum.
"Even if we leave our houses again we're afraid that gangs will loot everything in the house … we are living a nightmare of fear and poverty."
The army has mainly used air power and heavy artillery as it tries to drive back the RSF, which spread out across large areas of Khartoum and its adjoining cities of Bahri and Omdurman across the Nile after fighting erupted on April 15.
Violence has also flared in Darfur in western Sudan and in North Kordofan State, and other parts of the country, but the power struggle has been focused on the capital.
Both army chief Abdel Fattah al-Burhan and RSF commander Mohamed Hamdan Dagalo, known as Hemedti, are thought to have remained in Khartoum throughout the fighting.
According to latest estimates, more than 840,000 people have been displaced within Sudan and over 220,000 have fled to neighboring countries.
The U.N. World Food Program said it was ramping up its operations across at least six states in Sudan to assist 4.9 million vulnerable people, as well as assisting those fleeing to Chad, Egypt and South Sudan.
"The fighting in Sudan is devastating lives and livelihoods and forcing people to flee their homes with nothing but the clothes they are wearing," WFP East Africa director Michael Dunford said in a statement.
The U.N. said on Wednesday that more than half of Sudan's 46 million population needed humanitarian assistance and protection, launching a $3 billion aid appeal. It also said it had received reports of "horrific gender-based violence" in Sudan.
The aid effort has been hampered by the deaths of some humanitarian workers early in the conflict and repeated cases of looting.
The latest conflict broke out after disputes over plans for the RSF to join the army and over the future chain of command under an internationally backed deal for a political transition towards civilian rule.
Talks mediated by the United States and Saudi Arabia in Jeddah have so far failed to secure a ceasefire.