People living in the isolated north of Gaza have told the BBC that children are going without food for days, as aid convoys are increasingly denied permits to enter. Some residents have resorted to grinding animal feed into flour to survive, but even stocks of those grains are now dwindling, they say.

People have also described digging down into the soil to access water pipes, for drinking and washing.

The UN has warned that acute malnutrition among young children in the north has risen sharply, and is now above the critical threshold of 15%.

The UN’s humanitarian coordination agency, Ocha, says more than half the aid missions to the north of Gaza were denied access last month, and that there is increasing interference from Israeli forces in how and where aid is delivered.

It says 300,000 people estimated to be living in northern areas are largely cut off from assistance, and face a growing risk of famine.

A spokesman for the Israeli military agency tasked with coordinating aid access in Gaza said in a briefing last month that there was “no starvation in Gaza. Period.” The agency, Cogat, has repeatedly said it does not limit the amount of humanitarian aid sent to Gaza.

Mahmoud Shalabi, a local medical aid worker in Beit Lahia, said people had been grinding grains used for animal feed into flour, but that even that was now running out.

“People are not finding it in the market,” he said. “It’s unavailable nowadays in the north of Gaza, and Gaza City.”

He also said stocks of tinned food were disappearing.

“What we had was actually from the six or seven days of truce [in November], and whatever aid was allowed into the north of Gaza has actually been consumed by now. What people are eating right now is basically rice, and only rice.”

The World Food Programme (WFP) told the BBC this week that four out of the last five aid convoys into the north had been stopped by Israeli forces, meaning a gap of two weeks between deliveries to Gaza City.

“We know there is a very serious risk of famine in Gaza if we don’t provide very significant volumes of food assistance on a regular basis,” said the WFP regional chief, Matt Hollingworth.

The UN Office for the Coordination of Humanitarian Affairs (Ocha) said there had been a sharp increase in the number of aid missions denied access to northern Gaza: with 56% of deliveries denied access in January, up from 14% in October to December.

It also said the Israeli military “at times required justifications” for quantities of fuel destined for health facilities, and “imposed reductions on the volume of assistance, such as the quantity of food”.

The BBC asked Israel’s army for a response. They directed us to Cogat, which told us to address our questions to the army.

Duha al-Khalidi, a mother of four in Beit Lahia, told the BBC two weeks ago that she walked six miles (9.5km) to her sister’s house in Gaza City, in a desperate search for food, after her children had not eaten for three days.

“I don’t have any money, and even if I did, there’s nothing in the town’s main market,” she said. “[My sister] and her family are also suffering. She shared with me the last amount of pasta in her house.”

A famine risk assessment, carried out by several UN agencies, estimated that almost a third of residents in northern areas could now be facing a “catastrophic” lack of food, though restrictions on accessing the area make real-time measurements very difficult.

Families in northern areas are also struggling to find reliable water supplies.

“Many of us are now drinking unpotable water. There are no pipes; we have to dig for water,” explained Mahmoud Salah in Beit Lahia.

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