Israeli Prime Minister Benjamin Netanyahu has said a deadly strike on a displacement camp in Gaza's Rafah was a "tragic incident" that his government is "investigating".
"In Rafah, we evacuated a million uninvolved residents, and despite our best efforts a tragic incident happened yesterday (Sunday)," Mr Netanyahu told parliament.
He added that "we are investigating the case and will draw the conclusions".
The United Nations Secretary-General condemned the attack that "killed scores of innocent civilians who were only seeking shelter from this deadly conflict".
"There is no safe place in Gaza. This horror must stop," Antonio Guterres said in a social media post.
The UN Security Council is to hold an emergency meeting tomorrow to discuss the strike.
Diplomats said the closed-door meeting was requested by Algeria, which is a non-permanent member of the council.
The airstrike triggered a massive fire killing 45 people in a tent camp in the Gaza city of Rafah, according to Gaza officials, prompting an outcry from global leaders who urged the implementation of a World Court ruling to halt Israel's assault.
In scenes grimly familiar from a war in its eighth month, Palestinian families rushed to hospitals to prepare their dead for burial after the strike last night which set tents and rickety shelters ablaze.
Women wept and men held prayers beside bodies in shrouds.
"The whole world is witnessing Rafah getting burnt up by Israel and no one is doing anything to stop it," Bassam, a Rafah resident, said via a chat app, of the strike in an area of western Rafah that had been designated a safe zone.
Israeli tanks are continuing to bombard eastern and central areas of the city in southern Gaza, killing eight people, local health officials said.
Israel's military said that yesterday's air attack, based on "precise intelligence", had eliminated militant group Hamas' chief of staff for the second and larger Palestinian territory, the West Bank, plus another official behind attacks on Israelis.
Iit had said eight rockets were intercepted after being fired from the Rafah area. A minister said that showed the need for continued operations against Hamas.
Israel's top military prosecutor, however, called the airstrike "very grave" and said an investigation was under way.
"The IDF (Israel Defence Forces) regrets any harm to non-combatants during the war," Major-General Yifat Tomer Yerushalmi said at a conference.
The attack took place in the Tel Al-Sultan neighbourhood, where thousands were sheltering after Israeli forces began a ground offensive in the east of Rafah over two weeks ago.
More than half of the dead were women, children, and elderly people, health officials in Hamas-run Gaza said, adding that the death toll was likely to rise as more people caught in the blaze were in a critical condition with severe burns.
Israel has kept up attacks on Rafah despite a ruling by the top UN court on Friday ordering it to stop, arguing that the court's ruling grants it some scope for military action there.
By daylight, the camp was a smoking wreckage of tents, twisted metal and charred belongings.
Sitting beside bodies of his relatives, Abed Mohammed Al-Attar said Israel lied when it told residents they would be safe in Rafah's western areas. His brother, sister-in-law and several other relatives were killed in the blaze.
"The army is a liar. There is no security in Gaza. There is no security, not for a child, an elderly man, or a woman. Here he (my brother) is with his wife, they were martyred," he said.
"What have they done to deserve this? Their children have been orphaned."
Hospitals in Rafah, including the International Committee of the Red Cross field hospital, were unable to handle all the wounded, so some were moved to hospitals in Khan Younis further north in Gaza for treatment, medics said.
The UN agency for Palestinian refugees said the situation was horrifying. "Gaza is hell on earth. Images from last night are yet another testament to that," UNRWA wrote on X.
More than 36,000 Palestinians have been killed in Israel's offensive, Gaza's health ministry says. Israel launched the operation after Hamas-led militants attacked southern Israeli communities on 7 October, killing around 1,200 people and seizing more than 250 hostages, according to Israeli tallies.
Israel says it wants to root out Hamas fighters holed up in Rafah and rescue hostages it says are being held in the area.
Israel's army said its aircraft "struck a Hamas compound in Rafah", killing Yassin Rabia and Khaled Nagar, both senior officials for the Palestinian militant group in the West Bank.
It added that it was "aware of reports indicating that as a result of the strike and fire that was ignited, several civilians in the area were harmed. The incident is under review."
