A helpless mother tenderly cradles her emaciated son in a horrifying image encapsulating the “maelstrom of human misery” gripping Gaza. Muhammad Zakariya Ayyoub al-Matouq, one, weighs the same as a three-month-old baby, as famine slowly snuffs out life in the sealed-off enclave.

With bones protruding through his brittle skin and no help on the horizon, Muhammad has dropped from 9kg to 6kg (13lbs) because of an apocalyptic humanitarian crisis. Hunger and suffering has now reached a level never seen before with at least 12 children dying from malnutrition in the past 48-hours alone. The world has now united in calling for an end to the torment that has unfolded because of aid blockades.

Foreign Secretary David Lammy said: “I feel the same as the British public: appalled, sickened.

“These are not words that are usually used by a Foreign Secretary who is attempting to be diplomatic, but when you see innocent children holding out their hand for food, and you see them shot and killed in the way that we have seen in the last few days, of course Britain must call it out.”

Muhammad, clinging to life in a tent city with a black bin bag as a nappy, is one of 900,000 children in Gaza now suffering from hunger, with 70,000 in an advanced state of malnutrition.

Many face imminent death, as even hospitals are unable to provide food to patients because the final humanitarian lifelines have collapsed, as the world watches on.

The scarcity of water, milk, and basic necessities prompted United Nations Secretary-General António Guterres to say he is “appalled” at the accelerating breakdown of conditions in Gaza.

In an unprecedented intervention, he said he “deplores growing reports of children and adults suffering from malnutrition”, adding: “The population in Gaza remains gravely undersupplied with the basic necessities of life.”

After life-saving aid was initially let in, all crossings into Gaza have been closed since March 2, effectively halting a trickle of food, medicine, and aid, which has now almost completely dried up.

According to the latest UN situation report, already flimsy infrastructure is unable to cope with the daily arrival of severely malnourished people who, desperately clinging to hope, flock to medical points and hospitals.

Some 88% of Gaza is now under displacement orders or within displacement zones, with 1.3 million in urgent need of shelter. Yet no supplies have been allowed to enter for more than four months.

Sigrid Kaag, the UN’s senior humanitarian and reconstruction coordinator, said: “The war has not merely created a humanitarian crisis, it has unleashed a maelstrom of human misery.”

It is now thought that one-third of Gaza’s 2.1 million population has not eaten for several days, while one quarter faces famine-like conditions, with 100,000 women and children suffering from acute malnutrition.

Israel has banned international media from Gaza, so the world relies on reports from aid workers on the ground and unverified statistics from state-run institutions.

Gaza’s Hamas-run health ministry claimed 33 people, including 12 children, died in the past 48 hours.

The total number of deaths due to malnutrition since the start of the war with Israel now stands at 101, of which 80 are children.

One official with the United Nations Relief and Works Agency for Palestine said: “We’re in the death phase. Everything around people at the moment is death, whether it’s bombs or strikes; children are wasting away.

“Doctors and nurses who continue to work in clinics and medical centres are watching children disappear and die in front of their eyes, and there’s absolutely nothing that they can do about it.”

Aid workers hoped a fragile ceasefire in January, the first chance in 15 months to deliver food, shelter, water, and medical care, would allow them to scale up operations. But they are now increasingly fighting a lost cause.

The UN Human Rights Office says it has recorded 1,054 people killed in Gaza while trying to get food.

It said: “Our data is based on information from multiple reliable sources on the ground, including medical teams, humanitarian and human rights organisations.”

Ross Smith, World Food Programme director of emergency preparedness and response, added: “The hunger crisis in Gaza has reached new and astonishing levels of desperation. It’s one of the greatest tragedies we’ve seen.”