Prime Minister David Cameron promised to mount a "full investigation" into Friday's attack on a beach resort near the city of Sousse with 16 British detectives already in Tunisia to aid the police there.
Hundreds more British police were sent to interview tourists who have been returning to Britain from Tunisia, some of whom might have witnessed the beach massacre claimed by the Islamic State group.
"We will not give up our way of life and cower in the face of terrorism," Cameron said, underlining the need both to fight IS jihadists in Iraq and Syria and to tackle non-violent extremists in Britain.
Britain is to hold a minute's silence on Friday for the one-week anniversary of the attack, the worst for the country since four suicide bombings in London on July 7, 2005 killed 52 people.
US President Barack Obama expressed condolences in a phone call to Cameron, and said his country "stood firmly by" Britain, a spokeswoman for the prime minister said.
Flags were flown at half mast over Cameron's Downing Street office in sympathy with the victims, and amid fears of a heightened risk of attack, Britain is to hold a major emergency response exercise in London over the next two days.
The confirmed death toll of Britons is currently at 18 out of the 38 foreign tourists who were mowed down by a Kalashnikov-toting gunman, identified as 23-year-old student Seifeddine Rezgui.
Tunisia says four other victims have been identified as tourists from Germany, Portugal, Ireland and Belgium. Ireland said Sunday three of its citizens were killed.
A Royal Air Force (RAF) Boeing C17 plane evacuated four injured Britons on Monday and all 25 of the British wounded -- out of a total of 39 hurt -- will have been brought back by Tuesday, officials said.
Among the Britons killed was former Birmingham City footballer Denis Thwaites, 70, and his wife Elaine, the club announced on Twitter, saying it was "deeply shocked and saddened".
The RAF is ready to repatriate victims' bodies using in accordance with families' wishes using C17 and C130 military transport planes, according to the prime minister.
The government is pressing Tunisia to allow access for British experts to speed victims' identification.
Cameron said he shared the "frustration" of families waiting for news but noted the difficulty of the process as many tourists had not been carrying identification or were too disfigured.
Tour operators have laid on flights to evacuate tourists and the Association of British Travel Agents said about half of an estimated 20,000 British tourists in Tunisia at the time of the attack were now home.
British interior minister Theresa May travelled to Tunisia on Monday along with junior foreign minister Tobias Ellwood, who himself lost his brother in a terror attack on the Indonesian island of Bali in 2002.
source: www.abs-cbnnews.com
