Most of those killed when a gunman massacred holidaymakers on a Tunisian beach are feared to be British.
At least five of the 39 dead are British but that number is expected to rise substantially, Defence Secretary Michael Fallon has indicated.
They were killed by a 23-year-old student who disguised himself as a tourist and began firing at holidaymakers on a beach using a Kalashnikov he had hidden in a beach umbrella.
The student, identified as Abu Yahya al-Qayrawani, was reportedly laughing as he carried out the massacre and deliberately selected western tourists.
An eyewitness quoted by local radio said: "He was laughing and joking around, like a normal guy. He was choosing who to shoot. Some people, he was saying to them, 'You go away'. He was choosing tourists, British, French."
Terror group Islamic State claimed responsibility for the attack at the RIU Imperial Marhaba and the RIU Bellevue in the popular Tunisian resort of Sousse.
Mr Fallon told Sky News: "Sadly, we believe the majority are British of those who have been killed or injured. There are some victims who still have to be identified but the number, I'm sad to say, is going to increase."
Holiday firm Tui, which runs the Thomson and First Choice brands, confirmed that a number of those who died were its customers.
Speaking outside the TUI UK building near Gatwick Airport, Peter Long, joint CEO of Tui Group, said he was "deeply, deeply shocked".
"And our whole organisation is reeling with pain to see the suffering that has taken place in Tunisia."
He added that the company's directors from locations across the UK confirmed that so far it has repatriated 1,000 customers and that 5,400 still remained in the area, with everything being done to help those who wanted to return to get on flights.
However, the company was unable to confirm how many of its customers had been killed or injured in the tragedy.