KHARTOUM, Sudan - Fighting between forces loyal to Sudan's rival generals on Friday rocked the western region of Darfur, witnesses said, on the fourth day of a fragile U.S.-and Saudi-brokered cease-fire.

The one-week truce, the latest in a series of agreements that have all been systematically violated, was breached only minutes after it took effect on Monday night.

There have since been further violations of the cease-fire - which is meant to allow much-needed humanitarian aid to reach war-ravaged parts of the country - with the warring sides blaming each other.

In El Fasher, the capital of North Darfur, residents reported 'battles with all types of weapons,' six weeks into a war between the regular army, led by Abdel Fattah al-Burhan, and the paramilitary Rapid Support Forces (RSF).

Millions face famine

Since it erupted on April 15, the fighting has killed more than 1,800 people, according to the Armed Conflict Location and Event Data Project.

The United Nations says more than 1 million Sudanese have been displaced, in addition to 300,000 who have fled to neighboring countries.

Patients wait outside the clinics at the Medani Heart Centre hospital in Wad Madani, the capital of the Al-Jazirah state in east-central Sudan, on May 25, 2023.

Even before the conflict began, one-third of Sudan's 45 million people faced famine; about 25 million people are now in need of humanitarian aid, the U.N. said.

While the current cease-fire agreement has allowed for a lull in fighting, no humanitarian corridors have been opened to allow civilians to leave or aid to reach the affected areas.

Fighting in Khartoum, Darfur

The U.S. said on Thursday observers had detected the use of artillery, drones and military aircraft as well as fighting in Khartoum and in Darfur.

'We retain our sanctions authority and if appropriate we will not hesitate to use that authority,' said U.S. State Department spokesman Matthew Miller.

In Sudan's Capital, Residents Risk Death in Search of Water

Conditions have been particularly alarming in Darfur, already ravaged by a conflict that erupted in 2003 and saw then-President Omar al-Bashir unleash the feared Janjaweed militia to crush a rebellion among ethnic minority groups.

The RSF, which is led by Burhan's former deputy Mohammed Hamdan Daglo, traces its origins to the Janjaweed.

Burhan and Daglo had in 2021 staged a coup that unseated a civilian transitional government but later fell out in a bitter power struggle.