By Agencies

Yemen could see 250,000 cholera cases within six months, as death toll rises to 242, World Health Organization says.

Nearly 23,500 suspected cases of cholera have been registered in war-ravaged Yemen in the past three weeks, the World Health Organization said, as the death toll of the outbreak climbed to at least 242.

"The speed of the resurgence of this cholera epidemic is unprecedented," Nevio Zagaria, WHO country representative for Yemen, told reporters in a conference call on Friday.

Zagaria warned that there could be as many as 250,000 cases in the country within six months.

READ MORE: State of emergency in Yemen's Sanaa over cholera crisis

On Sunday, a state of emergency was declared in Yemen's opposition-held capital, Sanaa, after the outbreak killed scores of people over a two-week period.

The health ministry of the Houthi government announced the measure, saying that "the number of casualties surpassed the normal rates, exceeding the capacity of the health system, which has become unable to contain this unprecedented health and environmental disaster".

Humanitarian crisis

This is the second outbreak of cholera in less than a year in Yemen, the Arab world's poorest country in the grip of a war between government forces, which are backed by an Arab coalition, and Houthi fighters.

More than 10,000 people have been killed and millions displaced in more than two years of war, which has also destroyed much of the country's infrastructure.

Only a few medical facilities are still functioning and two-thirds of the population are without access to safe drinking water, the UN has said.

"What is happening today exceeds the capabilities of any healthy health system, so how can we [cope] when we are in these difficult and complicated conditions," Saba news agency quoted Mohammed Salem bin Hafeedh, Yemen's health minister, as saying.

The health ministry - after holding talks in Sanaa with Jamie McGoldrick, the UN humanitarian coordinator, and other international officials last week - called on humanitarian organisations and aid donors to help it avert an "unprecedented disaster".

What is cholera?

Cholera is an acute diarrhoeal disease that is transmitted through contaminated drinking water. It can be fatal within hours if left untreated.

Most sufferers exhibit mild symptoms that can be treated with oral rehydration solution, but the disease can kill within hours in severe cases if not treated with intravenous fluids and antibiotics.

In December, UNICEF said at least one child dies every 10 minutes in Yemen because of malnutrition, diarrhoea and respiratory-tract infections.

READ MORE: Cholera kills 115 people from late April to May, says ICRC

A cholera epidemic late last year petered out but outbreaks are becoming more frequent.

Sanaa has been worst hit, followed by the surrounding province of Amanat al-Semah, WHO data has shown. Cases have also been reported in other major cities including Hodeidah, Taiz and Aden.

About 17 million of Yemen's 26 million people lack sufficient food and at least three million malnourished children are in "grave peril", according to the UN.