Scotland Yard's counter terror chief has warned that the Islamic State group harbors ambitions of "enormous and spectacular attacks," as jihadis broaden their plots to target Western lifestyles.

Metropolitan Police Assistant Commissioner Mark Rowley told reporters Monday that while IS once primarily attacked military and police targets, their aims are now more assertive.

Rowley says "you see a terrorist group which has big ambitions for enormous and spectacular attacks, not just the types that we've seen foiled to date."

He described a group that is shifting. While it had once largely been using propaganda to radicalize people to act in their name, it is now "trying to build bigger attacks."

He says the group is trying to bring jihadis trained in Syria into northern Europe to launch attacks.