There have been fierce clashes between the Sudanese army and the rival Rapid Support Forces in the capital Khartoum and neighbouring cities of Omdurman and Bahri, across the River Nile.
The military has continued to carry out air strikes and residents sheltering in their homes are hearing loud explosions.
Rights groups in Darfur say fighting around the city of el-Geneina over the last few days has left more than 350 people dead.
There have been widespread reports of Arab militias loyal to the RSF attacking, looting and burning homes.
Medics say the health system in Darfur has totally collapsed.
The two warring parties are meant to have been negotiating in Saudi Arabia but so far all commitments to protect civilians and allow humanitarian access have been broken.