By Lucy Manning, special correspondent, and Sean SeddonBBC News
BBCYahel, left, has been confirmed as dead. Mother Lianne, centre, was also killed - sister Noiya, right, is missing.A British teenager who went missing after Hamas's attack on southern Israel was murdered, her family have told BBC News.
Yahel, 13, disappeared after militants attacked Kibbutz Be'eri and killed her British-born mother Lianne.
Family members have now confirmed to BBC News that Yahel was also killed. Her sister Noiya, 16, and Israeli father Eli are still missing.
Yahel's family said she was "full of adventure and mischief".
In a statement to BBC News, they said: "Beautiful Yahel. A bundle of unbridled energy and joy, with a cheekiness that you could not help but smile at and a brain which was sharp as a tack.
"Full of adventure and mischief, we will forever miss her, but are grateful for the light she brought into our lives in the too short time she was with us."
Relatives based in the UK said the family visited at least once a year, and spoke of the "joy on [the girls'] faces as they ripped open gifts".
On Monday, Lianne's British family said she was "a beloved daughter, sister, mother, aunt and friend who enriched the lives of all those lucky enough to have known and loved her".
Lianne, 48, first moved to Israel as a volunteer on a kibbutz when she was 19, before relocating there permanently.
"She lived a beautiful life and will be sorely missed by the heartbroken family and friends she leaves behind," her family added.
The family has not released the girls' surname.
Yahel, pictured here with climbing and diving equipment, was described as "full of adventure"Raz Matalon, Eli's brother-in-law, said he had a great relationship with Yahel, who he described as the "funny one" of the girls in their family.
He told the BBC he was still holding out hopes the rest of the missing family members would be found safe, adding that he did not know how he was going to manage the funeral arrangements.
"Now I have to arrange the funeral of... Lianne and Yahel and I don't know even how to do it because I never did one funeral. How can you arrange two or three or four? What do you say?"
He called on Prime Minister Rishi Sunak to visit Israel like the leaders of the US, France and Germany had, adding: "I think it's the right thing to do."
WhatsApp messages seen by the BBC reveal the chaos that engulfed the Be'eri community when Hamas militants began targeting southern Israel with rockets at around 06:30 local time on 7 October.
Lianne messaged family members to say she could hear gunfire and shouting in Arabic nearby. Living so close to the Gaza barrier, she was no stranger to security alerts. But "this is a whole other story", she told them.
Her husband's brother Yossi, his wife Nira, and their three daughters were also caught up in the attack.
Extended family members who were trying to contact their relatives in the kibbutz refrained from sending messages because they feared the sound of their phones could give them away if they were hiding from the gunmen.
Seven hours passed before they received word from Be'eri about the scale of the attack.
Yossi and one of his children have officially been declared as hostages.
Yahel, right, with sister Noiya, who is still missing
More on Israel Gaza war
Rishi Sunak said on Monday that "at least" six British citizens have died, with a further 10 people missing.
The prime minister said during a cabinet meeting on Tuesday that Hamas was responsible for the "murder and suspected abduction of British nationals", Downing Street said.
Asked if the government fears some of the 10 missing British citizens are being held captive, Mr Sunak's official spokesman said: "It's a dynamic situation.
"I think sadly the full details of this attack are still becoming clear."
International development minister Andrew Mitchell earlier told BBC Radio 4's Today programme the government was "extremely concerned" about missing British nationals in Israel.
He would not be drawn on whether discussions were taking place about the return of hostages via direct channels with Gazan authorities, but said the UK was doing "everything" it can to secure their release.
At least 1,400 Israelis were killed in the Hamas attack when gunmen infiltrated communities near the Gaza Strip.
More than 2,700 Palestinians have been killed in numerous air strikes against Gaza by the Israeli military that were launched following the attack.
Around 500 British nationals have left Israel in recent days on flights chartered by the British government.
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