David Cameron has revealed security services have foiled seven terror attacks on Britain in the past six months.
The Prime Minister told BBC Radio 4's Today show the attacks were on a smaller scale to Paris but is the "sort of thing we have been preparing for".
And he said if British interests were at stake then "we will act and take immediate action" in Syria and report to Parliament afterwards.
Britain is involved in bombing in Iraq but Cameron lost a parliamentary vote in 2013 to extend that action to Syria.
He added: "This is the struggle of our generation. This disease of Islamist extremist violence, this perversion of the religion of Islam that is being carried out by this minority, is a challenge we will have to face with everything we've got."
Samy Amimour, who was born in Drancy, a north-eastern suburb of Paris, is believed to be the first Paris attacker to be buried.
One of the cafes struck in the Paris terror attacks reopens as the city tries to move on in wake of the tragedy which claimed 130 lives.
Investigating judge in Belgium charges man with murder and participation in the activities of a terrorist organisation: reports