Foreign Office officials are assessing the situation in Israel and Gaza as the death toll continues to rise, with fierce fighting ongoing in the wake of an attack by Hamas.
Among the dead is 20-year-old Nathanel Young, a Briton serving in the Israeli Defence Services who died on the Gaza border on Saturday.
At least 700 people have reportedly been killed in Israel and more than 400 have been killed in Gaza, over two days after Hamas launched its unprecedented attack.
It comes as Israel intensified its bombardment of the Gaza Strip after declaring war and vowing to destroy the “military and governing capabilities” of Hamas.
Two other UK nationals – 26-year-old Jake Marlowe, who went to the same London school as Mr Young, and photographer Dan Darlington – are believed to be missing.
The Foreign Office has advised against all but essential travel to the region due to the conflict.
Mr Young, a former pupil at JFS Jewish School in north London, died after a surprise attack by Palestinian militants caught Israel off-guard on a major holiday.
His loved ones said they are “heartbroken”, while the father of Mr Darlington said he believes his son, who was visiting from his home in Berlin, Germany, is missing.
Mr Marlowe was reported missing while providing security at a music festival near Kibbutz Re’im, close to the Gaza border.
It comes as a Government minister warned any potential protesters not to “glorify” the violence of Hamas.
“Ultimately, there is a right to protest but there is not a right … to glorify terrorism.”
On Monday, Labour’s shadow chancellor Rachel Reeves also condemned the violence.
She said: “I want to see a Palestinian state existing alongside a safe and secure Israel.
“Terrorism is not the way to get there. I’m appalled by what we’ve seen.”
Ms Reeves told Times Radio: “Israel has been attacked by terrorists. It has every right to defend itself, get its hostages back and protect its citizens.”
All UK Government buildings were asked to light up in Israeli blue and white on Sunday evening, with the country’s flag projected on to the outside of No 10 in a show of support.