Israeli forces killed at least 33 Palestinians in the Gaza Strip Wednesday, health officials said, as troops deepened an incursion along the territory’s northern edge, bombarding a hospital and blowing up homes.Medics said at least 12 people were killed in an Israeli strike on a house in the area of Jabalia in northern Gaza earlier Wednesday, and at least 10 people remained missing as rescue operations continued.Another man was killed in tank shelling nearby, they said. Later yesterday, an Israeli air strike killed seven Palestinians, including a girl, in Al-Mawasi, in western Khan Younis in the southern Gaza Strip, Gaza medics said.Another air strike on a house in Remal neighbourhood in Gaza City killed four people, while a strike killed three Palestinians and wounded at least 20 others at a school sheltering displaced families in central Gaza Strip, medics said.Hussam Abu Safiya, director of Kamal Adwan Hospital in Beit Lahia, one of three medical facilities barely operational in the besieged northern area, said the hospital “was bombed across all its departments without warning.” Residents in the three towns - Jabalia, Beit Lahia, and Beit Hanoun - said forces had blown up dozens of houses. Israel’s 13-month campaign in Gaza has killed nearly 44,000 people and displaced nearly all the enclave’s population at least once.The World Health Organisation meanwhile expressed grave concern for hospitals still partly operating in war-stricken northern Gaza, where one hospital director described the situation as an "extreme catastrophe"."We are very, very concerned, and it's getting harder and harder to get the aid in. It's getting harder and harder to get the specialist personnel in at a time when there is greater and greater need," WHO spokeswoman Margaret Harris told journalists in Geneva.She said the organisation was "particularly concerned about Kamal Adwan Hospital" in Beit Lahia, where Israeli forces launched an offensive against Hamas and other Palestinian groups last month.Kamal Adwan Hospital director Hossam Abu Safiyeh told AFP by phone: "The situation in northern Gaza is that of an extreme catastrophe."We're beginning to lose patients because we lack medical supplies and personnel," he said.Abu Safiyeh added that his hospital had been "targeted many times by the occupation forces, most recently" on Monday."A large number of children and elderly people continue to arrive suffering from malnutrition," the doctor said.He accused Israel of "blocking the entry of food, water, medical staff and materials destined for the north" of the Gaza Strip.The WHO's Harris estimated that between November 8 and 16, "four WHO missions we were trying to get up to go were denied"."There's a lack of food and drinking water, shortage of medical supplies. There's really only enough for two weeks at the very best," she said.In its latest update on the situation in northern Gaza, the UN humanitarian office OCHA said Tuesday that "access to the Kamal Adwan, Al Awda and Indonesian hospitals remains severely restricted amid severe shortages of medical supplies, fuel and blood units".