Aid agencies have raised concerns as tens of thousands of people are expected to cross the Sudan border into Chad, which already hosts more than half a million refugees.
Aid workers operating at the border have described receiving an influx of people, mostly women and children, who had been walking for more than two days with little food and water.
The conflict in Sudan, between the armed forces and the powerful paramilitary Rapid Support Forces (RSF), has forced tens of thousands of civilians to evacuate to neighbouring countries such as Egypt, Chad, and Ethiopia.
More than 400 people have died and 3,700 have been injured after fighting broke out on April 15.
Since then, an estimated 20,000 people have entered Chad and at least 100,000 are set to arrive, the UN said earlier this week.
UNICEF and other aid agencies have warned that larger flows of refugees are expected to arrive
Concerns have been raised about the stability of the fragile region, with many of the population already struggling to access drinking water.
Anne Kathrin Schaefer, Internation Organization for Migration (IOM) Chad Chief of Mission, said: “The majority of those arriving are in dire need of basic humanitarian aid, namely food, water, and adequate shelter.
“We need the international community to urgently step-up financial support to help us provide a critical and rapid response to the growing needs.
“Unfortunately, the rainy season is around the corner, and it will render access to the border area complicated, making it even harder to provide relief to those who need it most.”
On Thursday, Africa Minister Andrew Mitchell warned that an end to the now-extended ceasefire could result in a humanitarian catastrophe in Sudan.
"It is essential that a ceasefire is maintained and that a political process is secured,” he told the foreign affairs think tank Chatham House.
"If not, the humanitarian consequences will be incalculable.”
The renewed ceasefire is due to end at midnight Sudan time (11pm BST) on 30 April, at which point violence could escalate.
Spokesman Jens Laerke of the UN Office for the Coordination of Humanitarian Affairs, said it has been forced to “reduce our footprint” because of the fighting.
He pointed to “acute shortages of food, water, medicines and fuel and limited communications and electricity” and new reports of looting of humanitarian warehouses and aid stockpiles.
“The humanitarian needs in Sudan were already at record levels before this recent eruption of fighting … some 15.8 million people - that’s about a third of the population - required humanitarian assistance,” he added.
Help and advice for people in Sudan or if you're worried about people in Sudan
If you are in Sudan you can contact the FCDO 24/7 helpline at +44 1908 516 666
Select option 2 for consular services for British nationals.
If you’re in the UK and worried about a British person in Sudan you can call 020 7008 5000.
FCDO advises against travel to Sudan for security reasons. More information can be found on the government website.
If you have not registered your presence in Sudan, you can register here.
You should also check the travel advice for Sudan for the latest guidance.
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