UNICEF's Yemen mission said that there had been an "alarming increase" in cholera-related deaths.
The agency's Yemen spokesman Mohammed Al-Asaadi told AFP that 3,000 new suspected cholera cases a day were being reported.
The International Committee of the Red Cross said Monday that 184 people had died of the disease since April 27, with 11,000 suspected cases across the country, AFP reported.
Cholera is a highly contagious bacterial infection spread through contaminated food or water.
UNICEF and the ICRC are part of a joint committee, also including the World Health Organization (WHO), that coordinates with health authorities and relief groups in Sana'a.
Authorities in the capital this week declared a state of emergency over the outbreak, the second wave of cholera cases in less than a year.
Hospitals are struggling to cope with the influx of patients.
Two years into a devastating war between the Houthis and government forces backed by a Saudi-led Arab military coalition, more than half the country's medical facilities are out of service.
Yemen's conflict has killed more than 8,000 people and wounded around 40,000, according to the WHO.
The UN has warned that two-thirds of the population is on the brink of famine.
The WHO now classifies Yemen as one of the worst humanitarian emergencies in the world alongside Syria, South Sudan, Nigeria and Iraq.