John Bacon

USA TODAY

The United Kingdom could face "an enormous and spectacular attack" from the Islamic State as the militant group broadens its efforts to disrupt life in the West, Britain's counterterrorism chief said Monday.

Scotland Yard Assistant Commissioner Mark Rowley said bigger, more damaging attacks are the next logical step for the Islamic State following the bloodbath in Paris last year that killed 129, the Telegraph and other media reported.

"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," Rowley said.

He said the Islamic State is trying to slip militants trained in Syria into Europe to conduct attacks.

Rowley said terrorism-related arrests throughout the United Kingdom in 2015 totaled a record 339. He said the number of arrests rose 57% in the last three years over the previous three years. About half of the arrests led to charges, he said.

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Last year, 77% of those arrested were British nationals, 14% were female, and 13% were under 21, the Telegraph reported.

The number of females has grown markedly in recent years, Rowley said.

"That would not have been the picture that one would have seen a few years ago," he said. "That is an indication of that radicalization, the effect of the propaganda and the way the messages ... are resonating with some individuals," he added.

Scotland Yard and MI5 have foiled three plots in London in the past few months, the Daily Mail reported.

Rowley said psychologists were involved in the counterterrorism effort amid concerns that people with mental health issues could be prime targets for Islamic State propaganda, the BBC reported.

The use of psychologists was becoming standard operating procedure, Rowley said, adding that "having that insight is critical."