Prime Minister David Cameron warned on Monday that Islamic State (ISIS) militants based in Syria and Iraq were planning specific attacks against Britain — similar to the attack in Tunisia last Friday that killed 30 British tourists — and posed an existential threat to the West.
Cameron's warning also came amid a report that criminal gangs have been smuggling powerful submachine guns, capable of firing 1,000 rounds a minute, into the country that could fall into the hands of would-be jihadists, The Telegraph reported.
A report from the National Crime Agency (NCA) published last week into serious and organized crime in the U.K. found evidence of an "increased threat" of Czech-made Skorpion submachine guns being imported by street gangs in London and across the southeast.
British security officials fear that these weapons could find their way into the hands of extremists intent on carrying out a terror attack, The Telegraph said.
The NCA report also warned that illegally held weapons and ammunition, often hoarded by collectors, could find their way into the hands of criminal organizations that might then pass them on to jihadists.
Counterterror officials have long been concerned over the crossover between ruthless criminal gangs and extremists.
Gun attacks similar to that carried out in Tunisia and the 2008 Mumbai atrocity are notoriously difficult for the authorities to derail because of the lack of planning needed to execute them.
On Friday, an Islamist gunman killed up to 30 British tourists on a beach resort in Tunisia, which British politicians have described as the single worst assault on their nationals since the bombing of the London underground in 2005.
"It is an existential threat because what is happening here is the perversion of a great religion and the creation of this poisonous death cult is seducing too many young minds," Cameron told BBC radio, Reuters reported.
"There are people in Iraq and Syria who are plotting to carry out terrible acts in Britain and elsewhere and as long as ISIL exists in those two countries we are at threat," Cameron said, using another acronym for ISIS.
Writing in The Daily Telegraph newspaper, Cameron signaled he wanted authorities to take a tougher line against Muslim extremists in Britain and to do more to challenge what he said were their unacceptable views.
"We must be more intolerant of intolerance — rejecting anyone whose views condone the Islamist extremist narrative," Cameron wrote.
Britain's international terror threat is currently set at "severe," its second highest level, and a rung which means an attack is "highly likely," Reuters said.
Scotland Yard is stepping up visible and covert policing at significant public events such as the Wimbledon tennis championships and planned services to mark the tenth anniversary of the July 7 attacks in London.
Assistant Commissioner Mark Rowley, National Police Chiefs' Council lead for counterterrorism, said the police response to the atrocity in Tunisia was likely to be one of the largest counterterrorism deployments seen since the 2005 attacks.
Reuters and The Telegraph were used in this report.