Six months into Israel’s war with Hamas, Israel’s “wounds” caused by the terror attack on Oct. 7 remain “unhealed,” U.K. Prime Minister Rishi Sunak said.

And Palestinians, including children, in the Gaza Strip need a humanitarian pause “immediately,” as well as a sustainable long-term cease-fire, Sunak said in a statement on Saturday.

“After six months of war in Gaza, the toll on civilians continues to grow — hunger, desperation, loss of life on an awful scale,” he said.

The U.K. continues to stand by Israel’s right to defend itself and defeat Hamas, he said, but he also called for the “terrible” conflict to end. The hostages must be released and aid must “be flooded in” to Gaza, he said.

“But the whole of the U.K. is shocked by the bloodshed, and appalled by the killing of brave British heroes who were bringing food to those in need,” Sunak said, referring to World Central Kitchen aid workers killed in Israeli military strikes.

The United Nations said it finally gained access to Gaza's largest hospital, Al-Shifa, following a days-long Israeli raid and found what the head of the World Health Organization called "an empty shell," with most buildings destroyed.

"The scale of devastation has left the facility completely non-functional, further reducing access to life-saving health care in Gaza. Restoring even minimal functionality in the short term seems implausible and will require substantial efforts to assess and clear the grounds for unexploded ordnance to ensure safety and accessibility for partners to bring in equipment and supplies," WHO said in a statement.

The WHO said its efforts to reach the hospital "to medically evacuate patients and staff and conduct an assessment were denied, delayed or impeded 6 times between 25 March and 1 April." According to the WHO at least 20 patients died due to lack of access to care.

The WHO said numerous shallow graves, and many partially buried bodies, were found just outside the emergency department after the Israeli siege.

"During the visit, WHO staff witnessed at least five bodies lying partially covered on the ground, exposed to the heat. The team reported a pungent smell of decomposing bodies engulfing the hospital compound. Safeguarding dignity, even in death, is an indispensable act of humanity," according to the WHO.

The destruction of Shifa and the main hospital in southern Gaza - Nasser - "has broken the backbone of the already ailing health system," the WHO said.

The people of Gaza are facing the "immediate prospect of a shameful manmade famine," United Nations Humanitarian Chief Martin Griffiths said, as he called for an end to the war.

"We have arrived at a terrible milestone," Griffiths said in a statement marking six months of the Israel-Hamas war. He called the prospect of further escalation in Gaza "unconscionable."

"Rarely has there been such global outrage at the toll of conflict, with seemingly so little done to end it and instead so much impunity," Griffiths said.

-ABC News' Nadine Shubailat

National security adviser Jake Sullivan will meet families of hostages at the White House on Monday, which is one day after the war reaches the six-month mark, a senior administration official said.

President Joe Biden on Friday wrote letters to the president of Egypt and the emir of Qatar on the state of the talks, and he urged them to secure commitments from Hamas to agree to and abide by a deal, the official added.

"The president made clear that everything must be done to secure the release of hostages, including American citizens, now held by Hamas terrorists for nearly six months," the senior administration official said.

"They discussed the importance of fully empowering Israeli negotiators to reach a deal, which in its first phase would secure the release of women, elderly, sick and wounded hostages," the official said.

A new round of talks will take place this weekend in Cairo.

-ABC News’ Selina Wang