"Health facilities supported by Save the Children across (Hudaydah) governorate recorded a 170 percent increase in the number of suspected cholera cases, from 497 in June to 1,342 in August," a report by the London-based NGO said.
In late July, Saudi-led "airstrikes resulted in the damage of a sanitation facility and water station that supplies Hudaydah with most of its water", the report said.
"After this incident, suspected cholera cases almost doubled" between July and August in health centers supported by the NGO, it said.
The United Nations and World Health Organization have warned Yemen faces a third cholera epidemic as autumn rains have increased the risk of infection.
Yemen has already been hit by two major cholera outbreaks in the past two years.
The WHO says 2,451 people have died of cholera across Yemen since April 2017, while more than a million suspected cases were reported during the same period.
More than 120,000 suspected cases were reported between January and mid-August 2018, according to the UN.
The Saudi-led coalition launched a major operation to retake Hudaydah from Yemeni forces in June.
Hudaydah's port is a vital lifeline for aid shipments to Yemen, the most impoverished country in the Arab world.
Yemen’s defenseless people have been under massive attacks by the coalition for more than three years but Riyadh has reached none of its objectives in Yemen so far.
Since March 2015, Saudi Arabia and some of its Arab allies have been carrying out deadly airstrikes against the Houthi Ansarullah movement in an attempt to restore power to fugitive former president Abd Rabbuh Mansour Hadi, a close ally of Riyadh.
The Yemeni Ministry of Human Rights announced in a statement on March 25 that the war had left 600,000 civilians dead and injured until then. The war and the accompanying blockade have also caused famine across Yemen.