At least 40 people have been killed in southern Gaza and dozens more injured in Israeli strikes on a designated humanitarian zone, the Hamas-run Civil Defence authority said.
The Israeli military said its aircraft attacked an operations centre in Khan Younis belonging to Hamas militants using precision weaponry.
Local residents said three strikes targeted tents housing displaced people in the humanitarian zone of al-Mawasi, west of the city of Khan Younis, causing huge craters.
"Forty people were killed and more than 60 injured, while many are still under the rubble," the operations director of Hamas's civil defence authority told the BBC.
Eyewitnesses told the BBC large explosions rocked the al-Mawasi area shortly after midnight and flames could be seen rising into the sky.
Khaled Mahmoud, a volunteer for a charity who lives near the site of the strikes, said he and other volunteers rushed to help but were stunned by the scale of the disaster.
"The strikes created three craters seven metres deep and buried more than 20 tents," Mr Mahmoud said.
Unverified videos showed civilians digging through the sand with their hands in an attempt to rescue Palestinians from a deep hole caused by the airstrikes.
Posting on Telegram, an Israel Defense Forces (IDF) spokesperson said it had attacked "key terrorists of the terrorist organisation Hamas who were operating in a command and control complex disguised in the humanitarian area in Khan Younis".
"Prior to the attack, many measures were taken to reduce the chance of harming civilians, including the use of precision weaponry, air strikes and additional intelligence information," the spokesperson added.
"This is another example of the systematic use by the terrorist organisations in the Gaza Strip of the population and civilian infrastructure, including the humanitarian space, for the purpose of carrying out terrorist acts against the State of Israel and the IDF forces."
Hamas rejected the Israeli military's claims that there were Hamas fighters present in the area, calling it a "blatant" lie.
"The resistance has denied several times that any of its members exist within civilian gatherings or using these places for military purposes."
Hundreds of thousands of displaced Palestinians have fled to Khan Younis since Israel launched its military campaign in the territory last October.
The ground operation was launched in response to Hamas's unprecedented attack on southern Israel on 7 October, in which about 1,200 were killed and 251 were taken hostage.
More than 40,900 people have been killed in Gaza since then, according to the territory's Hamas-run health ministry.