"We now are facing a serious outbreak of cholera," said ICRC director of operations Dominik Stillhart at a news conference in the capital Sanaa.
Citing figures compiled by the Yemeni health ministry, Stillhart said 115 people had died of cholera between April 27 and yesterday.
More than 8,500 suspected cases of the waterborne disease were reported in the same period in 14 governorates across Yemen, Stillhart said, up from 2,300 cases in 10 governorates last week.
Yemen is witnessing a devastating war between the Saudi- supported government and Iranian-backed Huthi rebels, and less than half of the country's health facilities are functioning two years into the conflict.
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Stillhart said hospitals were filled beyond capacity with patients displaying symptoms of cholera, a bacterial infection contracted through ingesting contaminated food or water.
"There are up to four cholera patients in one single bed," Stillhart said.
"There are people in the garden, and some even in their cars with the IV drip hanging from the window."
Critical food imports are also at an all-time low as many of the country's Red Sea ports are blockaded.
The United Nations has warned 17 million people - equivalent to two-thirds of the population - are at imminent risk of famine in Yemen.
More than 8,000 people have been killed since the Saudi- led Arab coalition intervened to support Yemen's government in 2015, according to the WHO.