Israeli strikes across Gaza killed 42 people on Wednesday as Israeli forces intensified a siege of northern parts of the Palestinian enclave, surrounding hospitals and refugee shelters, and ordering residents to head south, medics and residents said.

The Gaza health ministry and the World Health Organization said they would be unable to start a polio vaccination campaign in northern Gaza as planned because of the intense bombardments, mass displacements and lack of access.

Israeli forces began the operation in the north about three weeks ago with the declared aim of preventing Hamas fighters from regrouping.

The operation has intensified since the killing of Hamas chief Yahya Al-Sinwar a week ago.

Israel’s allies, including the United States, have said they hoped Sinwar’s death could provide a fresh impetus for peace by allowing Israel to declare that it had achieved some of its major objectives in Gaza.

But so far, Israeli forces seem to have only intensified their assault, especially on the northern areas, where Israel says Hamas fighters are regrouping in ruins of areas that were among the first targeted by Israel’s campaign last year.

The Israeli military announced last Friday it had sent another army unit to Jabalia on the northern edge of Gaza. Residents say the troops have besieged shelters, forcing displaced people to leave while rounding up many of the men.

The health ministry said at least 650 people had been killed since the new offensive began.

Of at least 42 people reported killed by Israeli military strikes across the enclave on Wednesday, 37 deaths were in northern Gaza.

The Gaza Civil Emergency Service said three of its rescuers were wounded in northern Gaza in what it said was a “targeted strike”, that aimed to force them out of Jabalia, hours after the Israeli army ordered some of their staff to leave the camp.

Later it said, all its operations in northern Gaza were suspended after Israeli forces detained five staff members and bombed the only fire truck.

“Our work has completely stopped in the North Gaza Governorate and the situation has become catastrophic there, and the citizens there are now without any kind of humanitarian services,” the civil emergency service said in a statement.

The United Nations Palestinian refugee agency UNRWA said on Wednesday one of its staff members was killed when an UNRWA vehicle was hit in Deir Al-Balah in the central Gaza Strip. Medics said the man’s brother was also killed.

The municipality of Gaza City said two city workers were killed and three others wounded in a strike there.

Health and civil emergency officials said dozens of bodies of Palestinians killed by Israeli fire in and around Jabalia were scattered on roadsides and under the rubble where medical teams could not reach them.

Hospitals in the north have either stopped providing medical services or are hardly operating because of the offensive. Hospitals where medics have refused Israeli evacuation orders say they are running out of blood for transfusions, as well as coffins and shrouds for the dead.

“We call on the world, which has failed to provide protection and shelter for our people and has been unable to deliver food and medicine, to make an effort to send shrouds for our fallen,” the Gaza health ministry said in a statement.

The polio vaccination campaign, launched after a baby was paralysed by the disease in Gaza for the first time in 25 years, had to be halted.

“We have not been able to launch the campaign to vaccinate 120,000 children in Gaza City and northern Gaza today because of the siege and the Israeli aggression,” health ministry official Majdi Dhair said.

Israel’s military humanitarian unit, COGAT, which oversees aid and commercial shipments to Gaza, said the vaccination campaign in northern Gaza will begin in the coming days, “after a joint assessment and at the request” of the World Health Organization and the U.N. International Children’s Emergency Fund UNICEF.

Call for truce

U.S. Secretary of State Antony Blinken visited Israel and was heading to Saudi Arabia to push for a ceasefire, the first major U.S. peace initiative since the killing of Hamas leader Sinwar and the last before a Nov. 5 presidential election that could upend U.S. policy in the region.

Washington has called on Israel to allow more humanitarian supplies into northern Gaza. Israel says aid has been delivered in scores of trucks as well as air drops, but Gaza medics say the aid has not reached them.

COGAT said on Tuesday that 237 trucks containing humanitarian aid from Jordan and the international community had been transferred to northern Gaza over the past eight days. Israel “will continue to act in accordance with international law to facilitate and ease the humanitarian response to the Gaza Strip,” it said.

Palestinian health officials and residents said no aid has been allowed into Jabalia, Beit Hanoun, and Beit Lahiya, three towns on the northern edge of Gaza.

The Israeli military said its forces were operating against Hamas militants who staged attacks from there, and that they killed scores of militants and destroyed military infrastructure while helping residents who heeded evacuation orders to leave.

The overall death toll in Gaza is approaching 43,000, according to the latest health ministry figures, and nearly all of the 2.3 million Gazans have been displaced, many multiple times.

The Israeli offensive was triggered by the Hamas-led attack on Israel on Oct. 7, 2023, in which 1,200 people were killed and around 250 taken as hostages back into Gaza.