An editorial "Paris attacks: It's war, but not as we know it" in the Independent said on Monday that "course of inaction is no longer possible".
"The danger of a Mumbai-style marauding terror attack in Britain has been understood by the security services ever since those dark days in India in 2008. Now, after Paris, we know what such an attack looks like. That's the sort of war we are in. We won't get out of it without a concerted effort," it said.
Over 160 people were killed in the November 2008 Mumbai terror attack that was carried out by 10 Pakistani gunmen who had sneaked into India.
The daily said that "there is only the naked dread that comes from knowing that the attacks can come at any time, from any direction, and that...these killers want and expect to die in the process, to become 'martyrs'."
"With the possible exception of chemical or biological attacks, it is hard to conceive of anything more frightening."
As many as 129 people were killed and 352 injured in a coordinated terror attack in Paris on November 13.
The daily said the fact that "this is war, in which we are all equally at risk, changes the response".
"Today, standing together is a simple necessity. Let the lesson sink in: we are up to our necks in a brutal conflict with an enemy of great strategic strengths, with abundant funding, a large home territory, thousands of troops..."
When horrible attacks occur, the temptation to resort to language inflation is strong, said the daily and added that in January, the Charlie Hebdo attack was described by some as "an act of war".
"That was hyperbole: the massacre at the satirical magazine's offices in Paris was a closely targeted assault on an ideological enemy of the Islamists."
President François Hollande used the phrase "an act of war" on November 13, "but this time he was right".
"Random but closely co-ordinated, the attacks were precisely an act of war, the closest that terrorists can approximate to the carpet bombing of enemy cities carried out in the Second World War," said the daily.
The daily noted that France has been disproportionately targeted, for reasons which are still being debated, but all countries which have been involved in fighting this enemy are at risk of similar attempts at retribution. "A co-ordinated and determined international response is now imperative."