The WHO warned last month that some 2,200 Yemenis have already died from the waterborne disease
The number of suspected cholera cases in war-torn Yemen has reached one million, the International Committee of the Red Cross said on Thursday.
"Yemen suspected cholera cases has reached the threshold of one million, amplifying the suffering of the country caught up in a brutal war," the ICRC said on its Yemen Twitter account.
The WHO warned last month that some 2,200 people have already died from the waterborne disease, which has propagated rapidly due to deteriorating hygiene and sanitation conditions.
Yemen is in the midst of a bloody war between pro-government forces and Houthi rebels who control the capital.
Saudi Arabia and its Arab allies intervened in the conflict on the side of the government in 2015 with air strikes and a far-reaching blockade on its neighbour's air and sea ports.
In early November, the coalition tightened that blockade in response to a missile fired by the Shia Houthis that was intercepted near Riyadh airport.
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At the time, the UN aid chief warned the move would exacerbate an already dire humanitarian situation.
The blockade was partially lifted three weeks later under massive international pressure, namely over the closure of Hudaida port - key to humanitarian and commercial deliveries.
The Iran-backed Houthis on Tuesday conducted another failed missile strike against Riyadh to mark the 1,000th day since the Saudi-led intervention.
The coalition said in a statement on Wednesday that it would not resort to closing Hudaida in the wake of the attack.
More than 8,750 people have been killed since Saudi Arabia and its allies joined the government's fight against the rebels, triggering what the UN has called the world's worst humanitarian crisis.