Gaza's civil defence agency said an Israeli strike on Friday night near Jabalia in the territory's north killed 33 people at a refugee camp.
Agency spokesman Mahmud Bassal announced "33 deaths and dozens of wounded" while a medical source at the Al-Awda hospital told AFP earlier that it had registered 22 dead and 70 wounded after the strike on the Tal al-Zaatar camp for Palestinian refugees.
Asked for comment about overnight strikes in the area, an Israeli army spokesperson said they were "looking into it".
On October 6, Israel launched a new offensive in northern Gaza, including around Jabalia, saying it was targeting Hamas fighters who were regrouping there.
Since then, scores of people have been killed in the area, which had already been hit hard by fighting earlier in the year-long war.
The UN humanitarian affairs agency said Friday night that it continued "to sound the alarm about the increasingly dire and dangerous situation that civilians in northern Gaza are facing. Families there are trying to survive in atrocious conditions, under heavy bombardment."
Israel accused of attacking hospital
Health authorities in Gaza said Israeli forces surrounded and shelled the Indonesian Hospital in the territory's northern town of Beit Lahia at dawn on Saturday.
"Israeli tanks have completely surrounded the hospital, cut off electricity and shelled the hospital, targeting the second and third floors with artillery," said the facility's director, Marwan Sultan.
"There are serious risks to medical staff and patients."
In a statement, Gaza's health ministry also said Israel had targeted the upper floors, adding there were "more than 40 patients and wounded in addition to the medical staff" present.
"Heavy gunfire" towards the hospital and its courtyard had sparked a "state of great panic" among patients and staff, it added.
Israel launched a new offensive in northern Gaza earlier this month, saying it was targeting Hamas fighters who were regrouping there.
Gaza's civil defence agency said an Israeli strike the night before in nearby Jabalia killed 33 people.
The UN humanitarian affairs agency on Friday continued "to sound the alarm about the increasingly dire and dangerous situation that civilians in northern Gaza are facing. Families there are trying to survive in atrocious conditions, under heavy bombardment."