The United Nations on Sunday made what it said was a record appeal for aid to Yemen, calling for nearly $3 billion in humanitarian relief for the war-torn country.

The $2.96 billion will be used to respond to an ever-broadening crisis in Yemen, where war, looming famine and cholera have killed thousands and put millions of lives at risk.

The appeal, made on behalf of UN agencies and humanitarian partners, came as 11.3 million people "urgently require assistance to survive", UN aid agency OCHA said in a statement.

"A generation of children is growing up in suffering and deprivation," OCHA said.

"Nearly two million children are out of school, 1.8 million children under the age of five are acutely malnourished, including 400,000 who suffer from severe acute malnutrition and are 10 times more likely to die if they do not receive medical treatment."

More than 9,200 people have been killed in Yemen since 2015, when a Saudi-led military coalition intervened to back the country's internationally-recognised government against Iran-backed rebels.

Another nearly 2,200 Yemenis have died of cholera amid deteriorating hygiene and sanitation conditions, the World Health Organisation says.

Over the past year, the United Nations' efforts to address what it has described as the world's worst humanitarian crisis have been hampered by a crippling blockade of rebel-held ports by the Saudi-led coalition.

More than three-quarters of Yemen's population -- 22.2 million people -- are now dependent on some form of assistance in Yemen, the United Nations says.

Some 8.4 million Yemenis are also at risk of famine, according to OCHA.

In 2017, international donors provided $1.65 billion of the $2.34 billion requested by the United Nations and humanitarian partners in Yemen.