A British man serving with the Israeli military has been killed in an attack by Hamas militants, his family says.
Nathanel Young had been serving with the Israel Defense Forces when he was killed on the Gaza border on Saturday.
The 20-year-old's brother, Eliot Young, said Nathanel had been "the life of the party" and was "loved by everyone".
Two other British citizens - Jake Marlowe and Dan Darlington - are missing in Israel following Saturday's attacks by Palestinian militants.
Mr Young's brother Eliot said: "Nathanel was full of life and the life of the party.
"He loved his family and friends and was loved by everyone."
He said Mr Young "loved music and was a talented DJ" and "always had strong Jewish pride".
The soldier was a "bubbly guy who his four nieces loved playing with", his brother added.
"When Nathanel could have taken his days off to sleep and re-energise, he instead found out where the family was, which wasn't always so close to him, and came to join us," his statement continued.
In a separate statement on Facebook, Mr Young's family said: "We're heartbroken to share that our little brother Nathanel Young was tragically killed on the Gaza border yesterday."
Mr Young was a former pupil at JFS, a Jewish school in Kenton, north London, the British newspaper Jewish News reported.
Labour leader Sir Keir Starmer said his thoughts were with Mr Young's family, as well as "all those whose families and communities have been touched by this terrible violence".
"Labour stands firmly in support of Israel's right to defend itself, rescue hostages and protect its citizens," he said. "The indiscriminate attacks from Hamas are unjustifiable and have set back the cause of peace."
Sir Keir added that "we will all stand firm against any intimidation or harassment directed towards Jewish communities here in Britain".
Meanwhile, Prime Minister Rishi Sunak said he had assured Israeli counterpart Benjamin Netanyahu of the UK's "steadfast support as Israel defends itself".
"We will do everything that we can to help. Terrorism will not prevail," he added.
Mr Sunak said the government was now working to establish the status of UK citizens in Israel, as he knows there will be "families who are anxious about their loved ones".
Missing Britons
Earlier, the Israeli Embassy in London confirmed London-born Mr Marlowe, 26, was missing and it was not known whether he had been taken hostage.
Mr Marlowe was working as security staff at an outdoor party near the Gaza border when he disappeared on Saturday.
His mother told Jewish News that she had spoken to him as the attacks were taking place.
"Then, at about 5.30am, he texted to say, 'signal very bad, everything OK, will keep you updated I promise you,' and that he loves me," she said.
She told the paper he lived in Ma'alot, in northern Israel, having moved to the country permanently two years ago.
The family of Mr Darlington also confirmed he was missing, telling the BBC they had not spoken to him since Saturday morning.
The photographer is originally from the UK but lives in Berlin, Germany, and had been visiting friends in Israel.
David Darlington, his father, said his son had been travelling with a German woman, and that his half-sister had last spoken to him on Saturday morning.
"The communications network is down and we haven't spoken to him for 24 hours," he said.
Saturday's surprise attack by hundreds of gunmen from Hamas has reportedly killed at least 600 people in Israel.
Hundreds of gunmen entered southern Israel, killing soldiers and civilians and taking into Gaza what the army said was a "significant number" of hostages.
Attendees of the music event near Kibbutz Re'im, where Mr Marlowe was working, have spoken of how gunmen opened fire at revellers in the early hours.
One attendee, Gili Yoskovich, told the BBC that she hid under a tree in a field as gunmen roamed around, shooting anybody they found.
The UK's Foreign Office said it was "in contact with - and assisting - the families of several individuals" in Israel and the Palestinian territories.
A spokesperson said they were aware of media reports regarding British nationals but would not discuss individual cases.