United Kingdom security officials said Britain is now "at war" following Saturday night's terror attack on London Bridge, and said intelligence gathering on Islamic extremists must be improved.

All main parties resumed campaigning for Thursday's general election on Monday, and many commentators said it was unlikely the attack would affect the result, as many people had made up their minds already.

"Make no mistake, we are now at war, and the way we handle intelligence has to change," a senior government official told China Daily. "Britain now faces two kinds of attack by these people - the carefully planned attack such as the Manchester suicide bombing, and those using vehicles and knives, which would appear to be more spontaneous."