Israeli military strikes killed at least 45 Palestinians across the Gaza Strip on Sunday, most of them in the north of the enclave, Palestinian health officials said, as efforts to secure a ceasefire in the more than year-long war resumed in Qatar.The directors of the CIA and Israel's Mossad intelligence agency will meet with Qatar's prime minister in Doha, an official briefed on the talks told Reuters.The death toll from Israel's campaign in Gaza is approaching 43,000, Gaza health officials say, with the densely populated enclave in ruins.At least 43 of those killed Sunday were in northern Gaza, where Israeli troops have returned to 'root out' Palestinian resistance (Hamas) fighters who it says have regrouped there.The United Nations said the plight of Palestinian civilians in northern Gaza was "unbearable" and the conflict was being "waged with little regard for the requirements of international humanitarian law"."The Secretary-General is shocked by the harrowing levels of death, injury and destruction in the north, with civilians trapped under rubble, the sick and wounded going without life-saving health care, and families lacking food and shelter, amid reports of families being separated and many people detained," UN spokesperson Stephane Dujarric said in a statement.Israeli authorities were hampering efforts to deliver food, medicine and other essential humanitarian supplies, putting lives at risk, he said. The devastation and deprivation resulting from Israeli military operations in the north were making life there untenable.Earlier Sunday, 20 people were killed following an airstrike on houses in Jabalia, the largest of the Gaza Strip's eight historic refugee camps, which has been the focus of an Israeli military offensive for more than three weeks.An Israeli airstrike on a school sheltering displaced Palestinian families in Shati camp in Gaza City, killed nine people and wounded 20 others, with many in critical condition, medics said.Three local journalists were among those killed at the school in Shati - Saed Radwan, head of digital media at Hamas Al-Aqsa television, Hanin Baroud, and Hamza Abu Selmeya, according to Hamas media.This raised the number of Palestinian journalists killed by Israeli fire since Oct 7, 2023 to 180, it added.Meanwhile, the death toll from an Israeli airstrike late on Saturday on a residential district in the nearby town of Beit Lahiya rose to 40, WAFA said.Israeli military strikes on the towns of Jabalia, Beit Hanoun and Beit Lahiya in northern Gaza have so far killed around 800 people during a three-week offensive, the Gaza health ministry said.