The terror threat posed by violent extremists has "evolved", one of the UK's most senior counter-terrorism officers has warned.
Mark Rowley, the Metropolitan Police Assistant Commissioner and national policing lead for counter-terrorism, said people are becoming increasingly radicalised by images they see online, with many "prepared to kill for their cause".
He said police have prevented "several attack plots" this year, but officers needed the public's help in protecting the UK from terrorists.
"They are no longer a problem solely stemming from countries like Iraq and Afghanistan, far away in the minds of the public," he said ahead of the launch of a nationwide terrorism awareness campaign.
"Now, they are home grown, in our communities, radicalised by images and messages they read on social media and prepared to kill for their cause.
"The tragic murder of Lee Rigby last year was a stark warning to us all about how real and local the threat is."
Mr Rowley's comments come after Met Police Commissioner Sir Bernard Hogan-Howe warned of the increasing terror threat and the possibility of a "lone wolf" attack on the streets of the UK.
Reports of suspicious behaviour have nearly doubled since the terror threat level was raised from "substantial" to "severe" in August but the public needed to be increasingly "vigilant", Mr Rowley said.
Rowley said "the eyes and ears of law enforcement and other agencies alone cannot combat the threat".
The terrorism awareness campaign will see officers briefing 6,000 people across the country on the threat and preventing attacks.
Sniffer dogs will be hunting large amounts of money at ports, airports and stations to prevent cash leaving the UK for terrorist purposes.
Farmers will also be advised on how to store their fertilisers - that can be used to make explosives - securely