Half of the terror plots disrupted in the UK in the past two years involved extremists who tried to buy guns, the national police chief for counter-terrorism has revealed.
Concerns about firearms falling into terrorist hands are running high amid a record level of gun seizures in London and similar spikes across a number of major British cities.
Mark Rowley, who is national policing lead for counter-terrorism, said there are potential links between street gangs and extremists when it comes to gun supply.
He said: "Half of the plots that have been disrupted in recent years have involved terrorist plotters who tried to get hold of guns.
"With terrorism you've got some vulnerable, lost people who just get hooked by an ideology.
"You've got some very bright, determined, clear-thinking people who buy into and fully commit and are drivers of Daesh (Islamic State) propaganda and terrorism, and then you do get gang members, criminals, people who are already angry, difficult people causing problems in communities who perhaps get given a more clear purpose for their violence by a terrorist ideology, whether they pick that up on the streets or in prison.
"Those gang criminality links are an issue that concerns us and we have seen evidence of it potentially linking firearms into terrorism."
At least 10 terrorist attacks have been foiled by British security services and police in the past two years.
On Monday the National Crime Agency (NCA) and counter-terrorism police launched a major campaign to try to clamp down on the supply of illegal guns into the UK.
NCA director Lynne Owens said that disrupting the supply of guns has "never been a more significant priority".
"Currently we believe we hold an advantage," she said.
"There is low availability of illegal firearms in the UK compared with European and international partners but it is not an advantage that we take for granted, and to maintain that advantage we must not stand still."
There are estimated to be about 750 organised crime gangs in the UK involved in firearms.
Last month, Britain's most senior police officer Sir Bernard Hogan-Howe warned more weapons were ending up on the streets of major UK cities, with a record 714 seized in London in 2015 and similar spikes seen in Manchester, Birmingham, Leeds and Liverpool.
Ms Owens said: "These criminal networks think nothing of who they supply their weapons to and they represent a significant risk or route by which an extremist or an extremist group will try to access the type of weapons that we did see used in attacks in Europe.
"One gun in the wrong hands in a public space is all it takes to cause devastation.
"The bottom line is that suppliers of commodity, be it people or drugs or firearms or encrypted Blackberries, will often sell it to the highest bidder. Organised crime is motivated by money.
"That's where we see an overlap, illegal firearms potentially coming into this country and being sold to whoever is willing to pay the biggest price."
Members of the public are being urged to pass information to police or Crimestoppers about guns being smuggled into the country or legally-owned weapons being stolen.