Early reports suggest multiple deaths and injuries after Yemen’s largest hospital, Al Thawra, was hit on Thursday, said Dr. Peter Salama, who is in charge of Emergency Preparedness and Response at the World Health Organization.

“We’re particularly saddened at WHO by the attack on one of the major hospitals in the country yesterday, Al Thawra in Al Hudaydah,” he said. According to latest news reports, at least 20 have been killed by several air strikes, which also hit a fish market in the city.

The attack on the hospital – which houses a major cholera treatment centre - is the latest outrage in the fight to capture the key Red Sea port from Houthi opposition militia.

The fighting is still raging and the ensuing humanitarian crisis has only deepened in a country that was already one of the world’s poorest, with some eight million people believed to be on the brink of famine.Yemen’s conflict has its roots in uprisings that date back to 2011, but fighting escalated in March 2015, when an international coalition led by Saudi Arabia intervened militarily at the request of President Abd Rabbuh Mansour Hadi. The coalition’s objective was to secure the return of the Government to the Houthi-held capital, Sana’a.

Sharing WHO’s condemnation of the Hudaydah attack, UN Humanitarian Coordinator for Yemen, Lise Grande, described the impact of the strikes as “appalling”.

Hospitals are protected under international humanitarian law, the UN official insisted, adding that “hundreds of thousands of people” depend on the hospital to survive.

“Everything that we are trying to do to stem the world’s worst cholera epidemic is at risk,” Grande said, noting that new cholera cases have been identified in the city “every day this week”.

In a bid to prevent the disease spreading once again, WHO’s Dr. Salama explained that combatants have been asked to down their weapons, so that an oral vaccination campaign can take place. More than 500,000 people are expected to receive the vaccine in a three-day operation beginning on Saturday.

“We have requested, as the UN, three days of tranquility, associated with, first, our cholera vaccine campaign across August 4, 5 and 6 in the north of the country,” Dr. Salama said. “You will recall that we were able to start campaigns in the south of the country previously, but we’ve never before been able to do it in the north.”

Asked to assess the level of risk from cholera, whose symptoms include watery diarrhea and fever, the WHO official said that the level of infection this year is “not at the same massive level” as last year.

Nonetheless, many people are far weaker than 12 months ago and far less able to cope with infection, he added.

“We’ve had two major waves of cholera epidemics in recent years,” Dr. Salama said, “and unfortunately the trend data that we’ve seen in the last days to weeks suggest that we may be on the cusp of the third major wave of cholera epidemics in Yemen.”