The explosion of cholera cases in war-torn Yemen is a "hideous milestone", according to the International Committee of the Red Cross.

Key points: Saudi-led blockade stopping medicines from reaching the affected

Saudi-led blockade stopping medicines from reaching the affected More than 80 per cent of Yemenis lack access to clean water

More than 80 per cent of Yemenis lack access to clean water UN also concerned by growing outbreak of diptheria

The number of suspected cases has now passed the 1 million mark, making it the worst cholera epidemic on record.

A desperate shortage of clean water, food and fuel left health authorities and humanitarian organisations in Yemen powerless to stop the disease.

The outbreak of cholera, which began in October 2016, has killed more than 2,200 people.

The Red Cross said more than 80 per cent of Yemen's population lacked access to clean water and medicine, largely because of a Saudi-led blockade on aid shipments into the country.

The United Nations said there was also a growing outbreak of diphtheria.

"These are medieval diseases," the UN's humanitarian coordinator in Yemen, Jamie McGoldrick, told the BBC.

"These are telling you that your systems are collapsing and people cannot buy the medicines, they cannot buy the goods that makes it easier to do that."

"Hind" was admitted to Al-Saba'een hospital for treatment for cholera and malnutrition.

Cholera is an acute infection spread by contaminated water or food that causes water diarrhoea, nausea, dehydration, fever and stomach cramps. In the worst cases it can kill within hours.

Humanitarian agency Oxfam's Yemen director, Shane Stevenson, said it was appalled at the impoverished country's horrifying new record.

"It is a disgrace that in the 21st century, an easy-to-treat cholera could infect over a million people in one country," Mr Stevenson said.

"This is the world's worst recorded outbreak, a man-made tragedy driven by more than a thousand days of a relentless and ruthless war.

"Month after month, the humanitarian situation in Yemen continues to deteriorate, slowly destroying every aspect of Yemenis' lives."

Oxfam said more than 16 million people — equivalent to two-thirds of Australia's population — were without clean water and millions more faced losing their supply unless the Saudi-led blockade was lifted quickly.

Alongside the cholera outbreak, up to 8 million Yemenis were on the brink of famine, in what the UN said was the world's worst humanitarian crisis.

Hospitals in the capital Sana'a and rural areas have been overflowing with malnourished children facing starvation.

Blockade prevents delivery of medicine

The war in Yemen this week passed 1,000 days. Since March 2015, Houthi rebels, backed by Iran, have been fighting a US-backed military coalition led by Saudi Arabia, which has been trying to reinstate the internationally recognised government ousted in 2014.

For months Saudi forces have imposed a blockade on Yemen's ports, preventing the delivery of food and health supplies.

But Saudi Arabia said on Wednesday it would open the port for a month to allow aid in.

Some of the medicine and aid available at a free pharmacy for patients with cholera in Yemen. ( Amy Hacker/Oxfam )

Aid agency Care said even a partial lifting of the blockade had not allowed aid to get through to where it was needed.

"Yemen's main ports must be allowed to open and function at full capacity to prevent full-scale famine and increased risk of disease," the agency said.

"There is no viable substitute for Hodeida Port [on the Red Sea].

"Almost 85 per cent of the population [22.8 million Yemenis] are typically supplied by imports from Hodeida Port. All alternatives to Hodeida Port have enormous implications in terms of cost, time and security.

"Aid shipments are not enough. Commercial goods must be allowed too."

The agency said humanitarian food aid was reaching only a third of Yemen's population. The remaining 18 million people rely on functioning commercial markets, which have been devastated by fuel scarcity and conflict.

The three-year war has killed more than 10,000 people in Yemen and displaced about 3 million.