The UN chief on Wednesday said "we failed" to stop war from erupting in Sudan, where persistent fighting between rival generals undermined efforts to firm up a truce.
"The UN was taken by surprise" by the conflict, because the world body and others were hopeful that negotiations would be successful, Antonio Guterres told reporters in Nairobi.
"To the extent that we and many others were not expecting this to happen, we can say we failed to avoid it to happen," the secretary general said.
"A country like Sudan, that has suffered so much... cannot afford a struggle for power between two people."
His remarks came as top UN humanitarian official Martin Griffiths was in Sudan one day after neighbouring South Sudan announced that the warring sides had agreed "in principle" to a seven-day ceasefire.
At least 550 people have been killed and 4,926 wounded, according to the latest health ministry figures, which are likely to be incomplete.
More than 100,000 refugees have fled to neighbouring countries in an exodus that has sparked warnings of a humanitarian "catastrophe" with implications for the entire region.
On Wednesday, Griffiths arrived in the Red Sea city of Port Sudan -- so far untouched by the fighting -- on an urgent mission to find ways to bring relief to the millions of Sudanese unable to escape.
Griffiths called for security guarantees "at the highest level" to ensure desperately needed aid deliveries to war-ravaged parts of the country.
"We know these general assurances need to be translated into specific commitments," he added.
On Tuesday the foreign ministry of neighbouring South Sudan announced that Burhan and Daglo "have agreed in principle for a seven-day truce from May 4th to 11th".
The two sides have yet to formally confirm the new ceasefire.
The warring sides have announced multiple truces but none has effectively taken hold. The current truce was extended on Sunday by a further 72 hours and is due to expire on Wednesday at 2200 GMT.
- Mounting condemnation -
Despite the truce efforts, witnesses reported warplanes over north Khartoum on Wednesday and fierce clashes near the state broadcaster's headquarters in the capital's twin city of Omdurman.
"We heard again loud gunfire and anti-aircraft firing at a fighter jet this morning," a resident of south Khartoum said.
Multiple hospitals have been among the facilities struck during the war, and the UN says only 16 percent of Khartoum's hospitals remain fully functional.
Saudi Arabia said the premises of its cultural centre in Khartoum were attacked on Tuesday "by an armed group which damaged equipment, cameras and seized some of the mission's property".
The kingdom condemned the raid, calling for de-escalation and an end to the violence.
Nearly 450,000 civilians have fled their homes, the International Organization for Migration said, including more than 115,000 who have sought refuge in neighbouring countries.
The border of Sudan's authoritarian neighbour Eritrea is now open to those fleeing, the Sudanese embassy in the country said, adding that those arriving by plane would be granted visa-free entry.
The failure of the warring generals to abide by their commitments in efforts to end nearly three weeks of fighting has drawn mounting international criticism.
He said the persistent fighting "compounds and complicates the political, security and humanitarian situation on the ground making it harder to resolve."
Egyptian President Abdel Fattah al-Sisi warned on Tuesday that the fighting in neighbouring Sudan was affecting "the entire region".
The Saudi-headquartered Organisation of Islamic Cooperation on Wednesday held an emergency meeting to discuss the situation in Sudan.
Griffiths also called for the lifting of "bureaucratic impediments to delivering assistance", pointing out that even he had had difficulty obtaining visas for his trip.
Of the more than 330,000 people displaced inside Sudan, more than 70 percent were reported to be from West and South Darfur states, according to the International Organization for Migration.
Darfur is still scarred by a war that erupted in 2003 when then-strongman Omar al-Bashir unleashed the Janjaweed militia, mainly recruited from Arab pastoralist tribes, against ethnic minority rebels.
The Janjaweed -- whose actions led to war crimes charges against Bashir and others -- later evolved into the RSF.
bur/it
© Agence France-Presse
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