Gaza is experiencing a health catastrophe that will last for generations to come, the director-general of the World Health Organization (WHO) has warned.
Dr Tedros Adhanom Ghebreyesus told BBC Radio 4's Today programme that a massive increase in aid is needed to begin to address the complex needs of the Strip's population.
Israel has allowed more medical supplies and other aid to cross into Gaza since a ceasefire with Hamas came into effect on 10 October, but Dr Tedros said levels are below those needed to rebuild the territory's healthcare system.
His intervention comes as the US attempts to shore up the ceasefire it helped to broker following an outbreak of violence at the weekend.
The agreement has been described by the White House as the first phase of a 20-point peace plan that includes an increase to the amount of aid entering Gaza, and supplies distributed without interference from either side.
Dr Tedros told the Today programme he welcomed the ceasefire deal but said the increase in aid that followed has been smaller than expected.
Asked about the situation on the ground, he said Gazans had experienced famine, overwhelming injuries, a collapsed healthcare system, and outbreaks of disease fueled by the destruction of water and sanitation infrastructure.
He continued: On top of that, [there is] restricted access to humanitarian aid. This is a very fatal combination, so that makes [the situation] catastrophic and beyond words.
Asked about long-term health prospects in Gaza, he added: If you take the famine and combine it with a mental health problem which we see is rampant, then the situation is a crisis for generations to come.
On Tuesday, the UN's World Food Programme said lorries carrying more than 6,700 tonnes of food had entered since 10 October, but that was still considerably below its 2,000-tonnes-a-day target.
Six hundred aid lorries a day need to be arriving in Gaza but the average is between 200 and 300, Dr Tedros said, as he called on Israeli authorities to de-link aid and the wider conflict.
Dr Tedros said aid should not be weaponised and called on Israel not to impose conditions on its delivery, including over the return of the remains of dead hostages still in Gaza, which has become a key point of contention during the ceasefire.
Israel launched a military campaign in Gaza in response to the 7 October 2023 attack, in which Hamas-led gunmen killed about 1,200 people and took 251 others as hostages.
In July, a UN-backed body concluded that famine had occurred in Gaza, though Israel disputed the findings, saying there was no starvation.
The UN has previously estimated it will cost $70bn (£52bn) to reconstruct Gaza. Dr Tedros said around 10% of that figure would need to be spent on its badly damaged health system.
He concluded: We have been saying for a long time that peace is the best medicine.
