Speaking at a press conference in London, Noam Sagi, 53, and Sharon Lifschitz, 52, both have parents who were taken hostage after Hamas attacked Israel on 7 October.

They said they were attending the conference as they must "fight" to get their loved ones back.

"I'm here because of pure evil", Mr Sagi, a London-based psychotherapist who grew up in Israel, said.

His mother, Ada Sagi, was taken from Nir Oz kibbutz, and is one of 97 people identified by Israel as having been taken after Hamas militants crossed the Gaza border. However, the actual number of hostages is believed to be more than 100.

"I shouldn't sit here today. I should have been on the way to Heathrow to pick up my mum who's coming to celebrate her 75th birthday here today in London," Mr Sagi said.

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Mr Sagi said he was attending the press conference to ask for help to release "babies, mothers, kids from their captivity".

He said the kibbutz where he grew up "woke up to a massacre" on Saturday, but he will "do everything I can for them".

'I ask for peace'

Ms Lifschitz said her 85-year-old mother was taken from her bed, alongside her 83-year-old father, in the Nir Oz kibbutz.

"My mum was taken out... she was disconnected from her oxygen, loaded onto a motorbike," she said.

"You have to be a special kind of person to take an 85-year-old woman from her bed.

"My father spent his life working for peace. I am his daughter. I ask for peace."

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"I'm not a military person, I'm not a politician. But at the moment it's the fact that we can't do anything before these elderly people and children come back," Ms Lifschitz said.

"The place is gone, the dead are dead," she said, adding "somewhere in Gaza there are children and mothers, and this is our fight now".

She said her community will be "dealing with this atrocity for the rest of our lives".

Seventeen British nationals are feared dead or missing in Israel, Sky News understands.

Jack Marlowe was a 26-year-old man who had been working as a security guard at a music festival when it was attacked by Hamas on Saturday. His family confirmed on Thursday that he had died.

Danny Darlington, who was originally from the UK and visiting, was due to leave Tel Aviv on Friday but had decided to stay and visit a kibbutz. He was murdered in Nir Oz on Sa

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The International Committee of the Red Cross - an impartial humanitarian body that visits prisoners of war and detainees and sometimes facilitates their release - said it was in direct contact with both Hamas and Israeli officials about the hostages but declined to give details.

It comes as Israel continues to strike the Gaza Strip, warning it will not break its siege until all hostages taken by Hamas are freed.

Israel has also suspended the supply of electricity, water and fuel to Gaza, plunging many Palestinians into darkness, with hospital supplies and fuel for emergency generators expected to run out within days.

Meanwhile, US Secretary of State Antony Blinken has said he will try to help secure the release of the hostages, during a joint press conference with Israeli Prime Minister Benjamin Netanyahu in Israel.

It followed a team of technical experts being sent to Israel by the US to advise and work with the Israelis on how to free people, an official source said on Wednesday.

At least 2,500 people on both sides have been killed over six days of fighting, with many anticipating an Israeli ground offensive.

However, IDF (Israeli Defence Forces) spokesperson Lt Col Richard Hecht said no decision has been made on a ground operation yet.