Ten bodies were brought to Kamal Adwan hospital and four to Al-Awda hospital, the two medical facilities reported.

The people were killed in an Israeli strike on the Abu Hussein school, which has become a shelter, in northern Gaza's Jabalia, where Israel's military says it is engaged in a sweeping assault targeting Hamas militants.

"A horrific massacre, most of the injured and wounded are lying on the ground at Kamal Adwan Hospital, and their condition is critical," said Fares Afana, a senior official at the ambulance and emergency service in north Gaza.

"We are unable to manage these severe cases due to the shortage of medical supplies and specialised personnel, leading to an increase in the number of martyrs."

The Israeli military said it had conducted a "precise strike" targeting militants from the Hamas and Islamic Jihad groups who had assembled at the school compound.

"At the time of the strike, dozens of terrorists from the Hamas and Islamic Jihad organisations were present in the compound," the military said, giving names of 12 Palestinian men it said were militants who were involved in rocket attacks against Israeli territory.

Hamas later condemned the attack.

"The occupation's claims that Abu Hussein School was used for resistance purposes are mere lies. This is a systematic policy of the enemy to justify its crime and slaughter of innocent displaced people," the group said in a statement.

Vast areas of Gaza have been devastated by Israel's retaliatory assault on the territory after an attack by Hamas on October 7 last year.

The Hamas attack resulted in the deaths of 1,206 people in Israel, mostly civilians, according to an AFP tally of official Israeli figures.

Israel's retaliation has killed at least 42,438 people, the majority civilians, according to figures from the health ministry in the Hamas-run territory, which the UN considers reliable.

Israel has been intensifying operations in the north of the besieged Palestinian territory, where the UN has warned hundreds of thousands of people are trapped.