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 6 October, 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."