Rescuers said a five-story residential building was hit, and videos on social media showed bodies covered in blankets on the floor, BBC reported.
The Israeli military conducted a brutal attack in northern Gaza during the past two weeks, particularly in the areas of Jabalia, Beit Lahia, and Beit Hanoun.
The director of the nearby Kamal Adwan Hospital in Jabalia, Hussam Abu Safia, told the AFP news agency that children were being treated at the hospital, which is struggling to treat patients due to a lack of staff and medicines.
"There is nothing left in the Kamal Adwan Hospital except first aid materials after the army arrested our medical team and workers," Abu Safia said.
State Department spokesman Matthew Miller said the US was "deeply concerned by the loss of civilian life in this incident. This was a horrifying incident with a horrifying result".
He pointed to "reports of two dozen children killed" in the attack.
The "tragic cost to civilians" in the latest strike "is another reminder of why we need to see an end to this war", Miller said.
The northern Gaza Strip faces a deepening humanitarian crisis, with hundreds of thousands of people living in desperate conditions.
UN human rights chief Volker Türk said on Friday that "the Israeli military is subjecting an entire population to bombing, siege and risk of starvation".
SD/