The United Nations estimates that 500,000 children are at risk of starvation in Yemen as the civil war threatens to escalate after months of a tenuous ceasefire.

The crisis has been brought on by the conflict, but also by skyrocketing food prices due to the conflict in Ukraine – the source of 40% of Yemen’s wheat.

In the southern city of Hodeida, dozens of children show up at a clinic every month, some of them showing signs of starvation, struggling to breathe and covered with sores.

Hunger has long threatened the lives of hundreds of thousands of Yemen’s children. Now, the war between the country’s Iran-backed Houthi rebels and a Saudi-led coalition is threatening to escalate.

Yemenis, as well as international assistance groups, worry that the situation will get even worse.

Joyce Msuya, UN assistant secretary-general for humanitarian affairs, said that in Hodeida, which has a population of roughly three million, al-Thawra Hospital receives 2,500 patients daily, including “super-malnourished” children. She visited the facility this month.

Around 2.2 million Yemeni children under the age of five are hungry. More than half a million are severely malnourished. Some 1.3 million pregnant or breastfeeding women had severe malnutrition this year, the United Nations says.

“This is one of the saddest visits I’ve ever done in my professional life,” Ms Msuya said in a video released by the UN.

“There are immense needs. Half of Yemeni hospitals are not functioning, or they are completely destroyed by the war. We need more support to save lives in Yemen, children, women and men.”

The war in Ukraine is exacerbating the situation.

The Yemeni diet depends heavily on wheat. Ukraine supplied Yemen with 40% of its grain, until Russia’s invasion cut the flow. In developed countries, people are working harder to pay higher bills.

In Yemen, food is 60% more expensive than it was last year. And in poor countries, inflation can mean death.

Peter Salisbury, a Yemen expert at the International Crisis Group, said: “Yemen has been hit three times by the Russian invasion of Ukraine.

“First, by the loss of food supplies from Ukraine and higher prices on international markets. Then, by higher fuel prices. And third, by a shift in international focus.”

War has raged for eight years in Yemen between Shia Houthi rebels and pro-government forces backed by a coalition of Sunni Gulf Arab states.

The Iran-backed Houthis swept down from the mountains in 2014, occupied northern Yemen and the country’s capital, Sanaa, and forced the internationally recognised government to flee into exile to Saudi Arabia.

Since then, more than 150,000 people were killed by the violence and three million were displaced. Two-thirds of the population get food assistance.

There is a truce in place now despite the two sides’ failure to renew it this month. More than half a million Yemeni children are severely malnourished. Every 10 minutes, a child in Yemen dies from preventable illness, according to Save the Children.

The children in Hays Hospital have swollen bellies and twig-like limbs. Eventually, prolonged malnutrition causes their organs to stop functioning, Dr Nabouta Hassan said.

Dr Hassan, who oversees the hospital’s malnutrition ward, said that every month it receives up to 30 children suffering from diseases related to acute malnutrition.

Hodeida, along with the northern province of Hajjah, includes the hardest-hit areas by extremely severe food insecurity and acute malnutrition, according to the UN.

The UN food agency has cut rations for millions of people due to critical funding gaps and soaring global food prices.

The World Food Program has for months prioritised the most vulnerable 13.5 million Yemenis, according to the UN Office for the Coordination of Humanitarian Affairs, or OCHA.

The UN said that by the end of September, its humanitarian response plan for Yemen secured two billion dollars (£1.7 billion) of the 4.27 billion dollars (£3.7 billion) needed to provide life-saving humanitarian assistance and protection services to 17.9 million people.

Abdulwasea Mohammed, advocacy, media and campaigns manager for Oxfam in Yemen, said his group needs more money, more consistent access to the most vulnerable, and a peaceful resolution to the conflict.

“The response is saving lives every day despite this,” he said.