A total of 9,908 cases have been recorded in the impoverished southern African country, the UN Office for the Coordination of Humanitarian Affairs said, raising an earlier toll of 389 dead out of 9,463 affected.
Warning of "alarming regional dimension," it said the health ministries of South Africa and Zimbabwe are striving to coordinate their efforts together with the World Health Organization.
"The rapid deterioration of the health service delivery system in Zimbabwe, lack of adequate water supply, and inability to dispose of solid waste and repair sewage blockages in most areas will continue to contribute to the escalation and spread of the outbreak," said OCHA spokeswoman Elisabeth Byrs.
Cholera is now hitting the whole of eastern Zimbabwe and spreading, she said, as UN humanitarian agencies aim to ensure delivery of medical supplies, clean drinking water and water purification kits.
Byrs said basic hygiene kits comprising a bucket or jerry can, soap and water treatment tablets have been distributed to at least 4,000 households in the Zimbabwean capital Harare.
UN Children's Fund (UNICEF) spokeswoman Veronique Taveau said that unlike previous outbreaks that mainly affected rural areas, the current epidemic is affecting densely-populated urban centres, "which leads to its rapid expansion and makes it harder to fight against the disease."
Jean-Philippe Chauzy of the International Organization for Migration said Zimbabweans fleeing deprivation in their country were contributing to spreading the disease.
South Africa has reported seven cholera deaths over the last two weeks, all Zimbabweans or people who had recently come from the country.
Phuti Seloba, health department spokesman in the South African border town of Musina, said that dozens of cholera patients from Zimbabwe enter the country every day.
South African health authorities have set up five cholera treatment centres along the border to handle the influx, he added.
Zimbabwe belatedly changed its tune Thursday and asked for international help to fight the outbreak after long insisting that the situation was under control.
"With the coming of the rainy season, the situation could get worse," said deputy health minister Edwin Muguti. "Our problems are quite simple. We need to be helped."