Airstrikes in Sudan’s western city of Omdurman have left 22 people dead drawing much condemnation from the UN secretary general.

According to Sudan's Health Ministry, the attack took place on Saturday, leaving at least 22 people dead and scores of others injured.

The Sudanese army, which has been fighting the paramilitary Rapid Support Forces (RSF) for 12 weeks now, claimed in a post on Facebook that its special forces had killed 20 "rebel soldiers" and destroyed their weaponry.

Hours later, the UN chief's spokesperson, Farhan Haq, released a statement, saying that in addition to condemning the air raid, António Guterres is appalled by reports of large-scale violence and casualties across Darfur region.

"He is also concerned about reports of renewed fighting in North Kordofan, South Kordofan and Blue Nile states. There is an utter disregard for humanitarian and human rights law that is dangerous and disturbing," the statement added.

It reiterated the UN's call for the Sudanese armed forces and the RSF to cease fighting and commit to a durable cessation of hostilities.

Sudan's army and the RSF have been fighting since April 15 over a power struggle between army chief, General Abdel Fattah al-Burhan, and his former deputy, Mohamed Hamdan Dagalo, who heads the paramilitary force.

More than 1,100 people have been killed in the fighting, which has flared in the capital in addition to Kordofan and Darfur regions, and has sparked ethnic violence in the West Darfur State.

More than 2.9 million people have been also displaced by the fighting, including nearly 700,000 who have fled to neighboring countries.

During recent days, fighting has focused on Omdurman because the western part of the city is used by the RSF as a key supply route to bring in reinforcements from Darfur, which is its main power base.

So far, most mediation efforts have largely failed and a few instances of temporary humanitarian ceasefire were violated by the warring factions.