The UK has announced it will expand its domestic and international spy agencies by recruiting 1,900 new intelligence agents in the wake of attacks in France and the Middle East.
David Cameron, UK prime minister, made the announcement on Monday during the G20 meeting of the world's leading economies in Turkey.
He called on the states to band together to cut off financing to proscribed entities, particularly the Islamic State of Iraq and the Levant (ISIL) group.
Speaking separately to BBC Radio 4, Cameron said the attacks in Paris on Friday, which left 129 people dead and hundreds more wounded, could have happened elsewhere in Europe, and the threat posed by ISIL and its supporters was widespread.
"Those attacks in Paris could have happened in Belgium, they could have happened in Denmark, it could have happened in Sweden, it could have happened here [UK]," he said.
"These extremists coming out of Syria and Iraq are radicalising our own citizens in our own countries, they want to cause the maximum damage to our countries and our way of life."
He said: "Here at this summit, we have agreed to take further important steps to cut off the financing that terrorists rely upon ... to counter the extremist ideology and the terrorists' propaganda ... and to better protect ourselves from the threat of foreign fighters, by sharing intelligence and stopping them from travelling."
In a transcript of the G20 summit speech released on the prime minister's website, Cameron said the UK would be doubling its spending on aviation security and stressed the need to provide financial assistance to countries with particularly vulnerable locations.
He said the fight against ISIL was the "struggle of our time".
British officials have previously claimed to have foiled a number of ISIL-inspired plots against the UK within the last six months.
The group, which controls large parts of Syria and Iraq, has repeatedly threatened the country and up to 600 British citizens are believed to have fought for the group.