Victoria Atkins, financial secretary to the Treasury, said the missing Britons were the government's "absolute priority".

"It's a very, very fast-moving situation, but the latest figure I've been given is that there are suspected to be six British nationals," she told Sky News.

Asked whether they were missing or being held hostage, she said: "We understand ... that they are hostages.

"I do acknowledge that it's a very fast-moving situation and that figure may or may not change, and I know how difficult that must be for the families and the friends at home here in the UK who are grappling with incredible worry and concern about their loved ones."

Ms Atkins earlier confirmed that the number of Britons killed either during or since Hamas's surprise attack on Israel had risen from nine to 10.

Israel-Gaza latest: Two female hostages freed by Hamas

Among the dead are two teenagers, a soldier, people visiting Israel on holiday, and a music festival security guard.

Hamas released two Israeli hostages on Monday night, after releasing two US citizens on Friday.

Yocheved Lifshitz and Nurit Cooper were taken from their homes by Hamas militants during the 7 October raids.

Sixteen days later, Hamas said it was releasing them for "humanitarian reasons".

Egyptian TV showed the women being taken out of Gaza at the Rafah crossing and put into ambulances.

The husbands of Ms Lifshitz and Ms Cooper are still being held hostage by Hamas.

The group did not explain why only the women had been released.

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American hostages Judith Raanan and her daughter Natalie Raanan were the first to be released by Hamas last week.

They too were let go for "humanitarian reasons".

Both of them hold Israeli citizenship and were on a trip to Israel from their home in Chicago to celebrate the Jewish holidays when they were seized.

Natalie Raanan's father said she was "doing very good" after her release.

On Sunday, before the release of Ms Lifshitz and Ms Cooper, a spokesperson for the Israel Defence Forces (IDF) said 212 people were being held hostage in Gaza.

One senior Hamas leader, Khaled Meeshal, told Sky News that the al Qassam Brigades - the armed wing of Hamas - had agreed that they would release the hostages.

He claimed that at least 22 hostages had been killed as a result of retaliatory air strikes by Israel - a figure Sky News has not been able to independently verify.

"Let them stop this aggression, and you will find that the mediators - like Qatar and some Arab countries like Egypt and others - they will find a way to have them released, and we will send them to their homes," he added.