The total figure is expected to be higher as other paramedic teams were working in the area.
Video aired on social media and by Israeli news outlets showed dozens of festival goers running through an open field as gunshots rang out. Many hid in nearby fruit orchards or were gunned down as they fled.
Militants began their assault from the sky, crossing the border on motorised paragliders.
Following the rampage, dozens of partygoers were reported to have been killed or kidnapped, with many more still missing.
The unconscious body of a dreadlocked female attendee was later paraded through Gaza in a truck, as passers-by spat on her. Among those reported to have been captured was a 26-year-old British citizen, Jake Marlowe, who was helping with security at the rave, the Daily Telegraph reported.
Partygoer Chen Mizrachi, a resident of Tel Aviv, told Israel’s Ynet news website: “It started at seven in the morning. When the rocket fire from the sky began, we started shouting “Code Red” to everyone (a warning used by Israelis for incoming rocket attacks from Gaza). There were several firing points; we ran from one direction to another.
“Many fell and were injured from terrorist fire ... Somehow, we managed to escape the line of fire. They shot at us three times during the escape.”
He and his friends eventually escaped, despite a rocket-propelled grenade hitting their car. “Gradually, I see friends I know arriving at the hospital. These are very, very difficult sights,” he added.
Gunmen stalked the festival site executing revellers, other witnesses said.
Gili Yoskovich told the BBC that she hid under a fruit tree, playing dead for three hours to dodge the gunfire and killings.
“I saw people were dying all around. I was very quiet. I didn’t cry, I didn’t do anything,’ she said.
“I was ... breathing, saying: ‘OK, I’m going to die. It’s OK, just breathe, just close your eyes’.”
She added: “They were going tree by tree and shooting. Everywhere. From two sides. I saw people were dying all around.”
By Sunday, reports were also emerging of partygoers being held in Gaza. Among those feared to be there was the British citizen Marlowe. According to Jewish News, a UK weekly newspaper, He had called his mother to say that the rave was under rocket attack and then texted her an hour later to say he loved her.
Tzipi Hotovely, Israel’s ambassador to the UK, told Sky News that she knew of “one British citizen who is in Gaza at the moment”, but did not say who it was.
The dreadlocked partygoer paraded through the streets of Gaza was reported to be Shani Louk, a German-Israeli dual national. CNN said it had verified a video showing her being driven in a truck guarded by a militant carrying a rocket-propelled grenade, while one of his comrades held her by the hair. Onlookers joined in with cheers of “Allahu Akbar” – Arabic for “God is great.”
In a video obtained by the German news outlet Bild, Louk’s mother Ricarda said: “This morning, my daughter, Shani Nicole Louk, a German citizen, was kidnapped with a group of tourists in southern Israel by Palestinian Hamas.”
“We were sent a video in which I could clearly see our daughter unconscious in the car with the Palestinians and them driving around the Gaza Strip. I ask you to send us any help or any news.”
A senior Hamas official says the militant group is holding more than 100 people captive after its unprecedented assault on Israel.
Mousa Abu Marzouk made the remarks to Arabic language news outlet al-Ghad on Sunday. The figure is in addition to more than 30 people said to be held by the Palestinian Islamic Jihad militant group.
During their rampage through southern Israel, militants dragged back into Gaza dozens of captives, among them women, children and the elderly. Their precise number hadn’t been clear until the two militant groups made their announcements.
The leader of Islamic Jihad, Ziad Nakhaleh, said in a televised speech Sunday night that their captives will not be released until all Palestinian prisoners in Israeli jails are set free, adding that Israel should acknowledge defeat.
Israel declares war
Israeli Prime Minister Benjamin Netanyahu’s office says his Security Cabinet has declared the country at war following a deadly Hamas assault in southern Israel.
The decision, announced on Sunday, formally authorises “the taking of significant military steps”, it said it a statement.
“The war that was forced on the State of Israel in a murderous terrorist assault from the Gaza Strip began at 06:00 yesterday,” it said.
It gave no further details. But Netanyahu had previously declared the country at war, and the military has promised a harsh response in Gaza, beginning by targeting the densely-populated area with air strikes.
Palestinian officials say more than 300 people have been killed by those strikes, without differentiating between fighters and civilians.
One of the strikes hit three homes in one of the most crowded refugee camps, Shaboura, killing 19 members of the same family, according to a family member who posted their names on his social media. Surviving family members and neighbours filled al-Farouk mosque, holding funeral prayers as the bodies of those killed wrapped in white shrouds lined the floor. The crowd then marched to the nearby cemetery for burial, some carrying the bodies.
Also on Sunday, loudspeakers from mosques and moving cars in Rafah blared with condolences and praise for fighters from Hamas, believed to be natives of Rafah, who were killed during the assault on Israel.