UN Secretary-General Antonio Guterres called on all parties to refrain from fighting in the al-Fashir area, a spokesperson said, adding that his envoy on Sudan was working to de-escalate tensions in the area.

The United Nations said Friday that it is increasingly concerned about a possible imminent attack on Sudan’s northern Darfur city of al-Fashir, home to 2 million people and about a half-million internally displaced, and is seeking to reduce tensions in the area.

A spokesperson for UN Secretary-General Antonio Guterres said in a statement that “The Rapid Support Forces [RSF] are reportedly encircling al-Fashir, suggesting a coordinated move to attack the city may be imminent. Simultaneously, the Sudanese Armed Forces [SAF] appear to be positioning themselves.”

“An attack on the city would have devastating consequences for the civilian population. This escalation of tensions is in an area already on the brink of famine,” the spokesperson added.

The statement said that the secretary-general’s personal envoy in Sudan, Ramtane Lamamra, is working with the parties to de-escalate tensions in al-Fashir.

War erupted in Sudan one year ago between the Sudanese army and the paramilitary RSF, creating the world’s largest displacement crisis.

Al-Fashir is the last major city in the vast, western Darfur region not under control of the RSF. The RSF and its allies swept through four other Darfur state capitals last year, and were blamed for a campaign of ethnically driven killings against non-Arab groups and other abuses in West Darfur.

At least 43 people, including women and children, have been reportedly killed in fighting in al-Fashir since April 14 when the RSF, backed by its allied militia, began a push to gain control of the city, the SAF’s last remaining stronghold in Sudan’s Darfur region.

Residents, aid agencies, and analysts say the fight for al-Fashir – a historic centre of power – could be more protracted, inflame ethnic tensions that surfaced in the early-2000s conflict in the region, and reach across Sudan's border with Chad.

Earlier on Friday, a spokesperson for the UN High Commissioner for Human Rights Volker Türk urged the parties to immediately halt violence in and around al-Fashir.

Seif Magango, speaking from the Kenyan capital of Nairobi, warned that the fight for al-Fashir – already raging outside the city for several weeks – may be taking a turn for the worse.

“Reports indicate that both parties have launched indiscriminate attacks using explosive weapons with wide-area effects, such as mortar shells and rockets fired from fighter jets, in residential districts,” Magango said.

The United States on Wednesday also called on all armed forces in Sudan to immediately cease attacks in al-Fashir.

Top UN officials warned the Security Council last week that some 800,000 people in the city were in “extreme and immediate danger” as worsening violence advances and threatens to “unleash bloody inter-communal strife throughout Darfur.”

The UN has said nearly 25 million people, half of Sudan’s population, need aid and some 8 million have fled their homes.

A UN-backed global authority on food security has said that immediate action is needed to “prevent widespread death and total collapse of livelihoods and avert a catastrophic hunger crisis in Sudan”.

Donors pledged more than $2 billion for war-torn Sudan at a conference in Paris last week.