A man kisses the Tunisian flag at the site of the Sousse shooting Getty

Britain in on alert for a possible terror attack in the wake of the Tunisia massacre following a rise in the number of sub-machine guns smuggled into the country.

The National Crime Agency (NCA) warned of the "increased threat" of Czech-made Skorpion weapons being brought in raising fears of a possible similar shooting to the one seen in Sousse on Friday 26 June, which killed at least 30 Britons.

The Skorpion, which was discontinued in 1979, was one of the weapons used by the gunmen in the Charlie Hebdo shooting which left 12 people dead as well as the attack on a kosher supermarket in Paris.

The NCA is now warning of the possible threat of jihadists and criminal gangs trading in these firearms. They are known to be sold for around £3,000 each on the black market.

The risk was outlined in the NCA's National Strategic Assessment, which states: "Handguns and shotguns remain the two types of firearms favoured by criminals. However, sub-machine guns (SMG) are also used by criminals, with an increased threat of Skorpion SMGs being imported into the UK destined for urban street gangs in south-east England."

It adds: "Significant detections and seizures continue to be made at UK borders."

In January, the Metropolitan Police described the Skorpions as "some of the most dangerous weapons ever seen reach the hands of UK criminals" after a prisoner and his girlfriend were convicted of running a gun smuggling operation from inside Wandsworth jail.

Scotland Yard has already said it is increasing patrols and security in the UK in the wake of the Tunisia attack, with the second week of Wimbledon also coinciding with the 10<sup>th anniversary of the London 7/7 bombings.

Assistant Commissioner Mark Rowley, National Police Chiefs' Council lead for counterterrorism, said: "The national policing response to the attack in Tunisia is likely to be one of the largest counterterrorism deployments seen since July 2005.

"The operation currently involves more than 600 officers and staff and is being coordinated from the National Counterterrorism Policing HQ at New Scotland Yard. Because of the scale of the attack, the numbers of fatalities and the international nature of it, it is likely that several hundred counterterrorism and other police officers and staff will be working on this case for some time.

"Since Friday evening [26 June], more than 380 counterterrorism and local officers have been at British airports to meet and support travellers returning from Tunisia to help identify potential witnesses. On Saturday, officers met 27 flights and there will be similar levels of activity today, including taking detailed statements from many witnesses to support the UK coronial process.

"Officers will remain at the airports to meet more returning citizens as and when they come home."

The Met has also deployed 16 officers to help with the investigations in Tunisia and offer support to the victims and their families. Home secretary Theresa May and foreign office minister Tobias Ellwood are also is heading out to Tunisia.

Elsewhere, prime minister David Cameron said the ongoing battle against the Islamic State (IS) will be the "struggle of our generation".

Speaking on the BBC Radio 4's Today Programme, he said: "It is an existential threat because what's happening here is the perversion of a great religion and the creation of this poisonous death cult that is seducing too many young minds in Europe, in America, in the Middle East and elsewhere."