Rishi Sunak has vowed that anyone in the UK supporting Hamas will be “held to account” in the aftermath of the attack on Israel.
The prime minister said the government was ready to support any British citizens in need of help, during a visit in Staffordshire on Tuesday.
A “significant number” of British-Israeli dual nationals have been caught up in the conflict in Israel and Gaza, the foreign secretary, James Cleverly, said earlier.
Sunak confirmed his support for Israel, saying he stood in solidarity with the state and its people “in the face of these barbaric acts of terrorism”.
Discussing his visit to a synagogue in north London on Monday night, Sunak said he had been “unequivocal with them that we will make sure that they feel safe at this time”.
He added that police had “been given very clear guidance and advice from the government to do everything that they can to keep the community safe”.
Officers will “clamp down on any behaviour that falls foul of the law”, Sunak said.
He added: “I’d just remind everyone that Hamas is a proscribed terrorist organisation. People should not be supporting Hamas and we will make sure that we hold people to account if they are.”
The number of Britons caught up in the violence in Israel and Gaza has yet to be confirmed, with ministers wary that official estimates of casualties and those injured are still being compiled.
Sunak said he understood there were families in the UK “anxious about their loved ones in the region”.
He continued: “I want to reassure them we’re doing everything we can, working very closely with the Israeli authorities to establish what is happening on the ground, provide support to people where it’s needed.
“I’d urge anyone there to contact the Foreign Office so that they have their details, follow the advice locally from the Israelis but also from the Foreign Office, and we stand ready to support everyone as best we can.”
Earlier, Cleverly called on supporters of Palestine to stay at home, after protests in London.
The foreign secretary said: “There is no need, there’s no necessity for people to come out. It causes distress. This is a difficult, delicate situation.”
He said the protests were causing concern in the Jewish community, “who have often been on the receiving end of prejudice and threats of violence”.
“There’s no need for this at all. I would encourage them just to pause.”
Fighting in the region is continuing, with the Israeli air force announcing on social media that it was planning to launch “an extensive attack against terror targets of the terrorist organisation Hamas in the Gaza Strip”.
The UN human rights chief said on Tuesday that Israeli air operations had struck residential buildings, including tower blocks, as well as schools and UN buildings across Gaza, resulting in civilian casualties.
Gaza’s health ministry said at least 770 Palestinians had been killed and 4,000 wounded by Israeli airstrikes since Saturday. They additionally claim that at least another 18 people have been killed and 100 injured in the West Bank since Saturday.