The risk of an ISIS terror attack in Britain is "very significant," Foreign Secretary Philip Hammond warned on Thursday.

According to Daily Mail, Hammond said Britains ought to be on the lookout to "disrupt ... plots before they come to the stage of an attack."

The country's top diplomat spoke ahead of a counter-terror summit in London where foreign ministers from around the globe are set to discuss strategies on how to take on Islamic militants and prevent attacks such as the Jan. 7 and Jan. 9 attacks in Paris. In those incidents, terrorists killed 12 at the offices of French satiric magazine Charlie Hebdo and four at a Kosher grocery store.

The Yemeni branch of al-Qaida, a group that refers to itself as "al-Qaida in the Arabian Peninsula," was the first to claim responsibility for the Charlie Hebdo attack, but ISIS, the terror organization that now calls itself Islamic State and controls large swaths of land in Iraq and Syria, similarly acknowledged involvement, CBS News reported.

"There's a very significant risk of an (ISIS)-inspired attack being planned and -- if we are not successful in intercepting it -- executed by (ISIS) sympathisers who live in the (United Kingdom) but are inspired by what is going on in Iraq and Syria," Hammond said.

The Independent reported Hammond also assured British citizens that security services were working under intense pressure to fight such terrorist threats.

"We know there are people out there who wish us harm, and we have to be vigilant and we have to work extremely hard to make sure we identify and disrupt these plots before they come to the stage of an attack," he said.

ISIS likely remains the "greatest single immediate threat to Britain's national security," Hammond concluded, but the secretary also pointed to the U.S.-led campaign of airstrikes, which he claimed have been "very effective" in containing the organization.

U.S. Marine Corps Gen. John Allen, who is coordinating international efforts to tackle ISIS, will brief foreign ministers at their London meeting.

Turkish Prime Minister Ahmet Davutoglu, meanwhile, warned that his country has been unable to close its 510-mile-long border with Syria. The flow of jihadi volunteers entering the civil war-ravaged country, whose north is an ISIS stronghold, may thus be "unstoppable," Davutoglu said.