Britain's most senior counter-terrorism police officer warned on Monday of the risk of further "spectacular" attacks by the Islamic State group as it trains its sights on "Western lifestyle" targets.

London Metropolitan Police Assistant Commissioner Mark Rowley said British police had carried out a record number of counter-terrorism arrests last year.

But he warned that the Islamist group had broadened its focus from military and police targets, noting the Paris attacks last year when gunmen attacked bars, a concert hall and a stadium, killing 130 people.

"In recent months we've seen a broadening of that, much more plans to attack Western lifestyle, and obviously the Paris attacks in November," Rowley told reporters.

"Going from that narrow focus on police and military as symbols of the state to something much broader.

"And 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."

Police have previously said they foiled seven plots between late 2014 and early 2016.

Across Britain, police made a record 339 arrests related to counter-terrorism in 2015, around half of which resulted in charges being brought.

Arrests in the past three years are 57 percent higher than in the previous three years.

Some 77 percent of arrests last year were British nationals, while 14 percent were female and 13 percent were aged 20 and under -- a new trend that reflects specific targeting by IS group jihadists of vulnerable groups on social media.

Britain has suffered only one fatal incident of international terrorism since the July 7, 2005 attacks on the London transport system that killed 52 people.

In 2013, two Muslim converts butchered soldier Lee Rigby near his London barracks in broad daylight.

Rowley said Britain had some advantages over other Western countries in fighting terrorism, notably its experience with dealing with paramilitary groups linked to the conflict in Northern Ireland and tough laws on gun control that made it difficult to obtain firearms.

The Metropolitan Police announced after the Paris attacks that it was training another 600 firearms officers, taking the total number to 2,800, out of a 31,000-strong force.

British authorities have since 2014 assessed the country's threat from international terrorism to be severe, the fourth of five levels meaning an attack is highly likely.