Terror threat in the UK rising as police report an 'exceptionally high' number of incidents

Planned extremist attacks in the UK connected to Isis are increasing in number, said the country's senior counter-terrorism official

The national threat level is at “severe” meaning a terrorist attack is “highly likely” (Getty Images)

The threat of a terrorist attack in Britain is at its highest point in years, with several plots “directed by or inspired by terrorism overseas” foiled so far this year, the country’s leading counter-terrorism official has revealed.

Speaking amidst fears that the Islamic State extremist group operating in Syria and Iraq is radicalising British youth, Scotland Yard Assistant Commissioner Mark Rowley said the number of incidents is “running exceptionally high”.

In an unprecedented move, Rowley, the National Policing Lead for Counter Terrorism, detailed the scale of the threat.

He said: "So far this year we have made 218 arrests and are running exceptionally high numbers of counter-terrorism investigations, the likes of which we have not seen for several years. Against an increasing operational tempo we are disrupting several attack plots a year.

"These plots are of varied sophistication, from individuals planning to carry out spontaneous yet deadly attacks to more complex conspiracies, almost all seemingly are either directed by or inspired by terrorism overseas. We have secured evidence and charged 16 returnees for terrorist activity in Syria.”

The senior officer's comments came after Scotland Yard made a series of arrests over an alleged "significant" plot cooked up by suspects including at least one man who was believed to have travelled to Syria.

Another series of swoops by counter-terrorism teams in the South East saw three men and three women arrested following raids at four addresses in Portsmouth and Farnborough in Hampshire, and Greenwich, south east London.

Hundreds of young Britons have flown to Syria to join Isis (Reuters)

The threat of a terrorist attack in the UK is at its highest since the aftermath of the 7/7 bombings in 2005, according to a source close to the Guardian.

Rawley reported that more than 1,000 pieces of extremist material are being removed from the internet by police every week, including videos of beheading, torture and suicides. Over 80 per cent of that material is related to Iraq and Syria.

He said: "The growing problem of young, impressionable, and in some cases vulnerable, individuals being radicalised online is an increasing risk. Extremist groups are using social media in highly sophisticated ways in order to recruit or persuade individuals towards their violent and warped ideologies.

"Dozens of families have contacted us concerned about loved ones or information when they believe someone is travelling abroad. It is only through courageous action like that that we can help and we have been supporting such families in every way we can."

So far there are 66 people who have been reported missing to police who are thought to have headed to fight in Syria.

There were also much publicised appeals to try to find missing teenagers Samya Dirie, 17, and Yusra Hussien, 15, who vanished last month and are thought to have travelled to the war-torn state.

Philip Hammond said that ministers are considering treason charges against the young Britons joining Isis (AFP)

Foreign Secretary Philip Hammond has said Britons who have become embroiled in the jihadi war in Iraq and Syria should be tried for treason.

The last prosecution for treason was in 1946, when the notorious Lord Haw Haw - real name William Joyce - was hanged for his Nazi propaganda broadcasts.

The offence remains on the statute books, even though the death penalty has been abolished.

Isis kills 50 in a wave of attacks on Baghdad

Chairman of the Home Affairs Select Committee Keith Vaz called the level of terrorist activity "disturbing".

He said: "These are startling figures much higher than anyone has feared. The sheer scale and level of activity is most disturbing. Internet companies need to continue to work with the police and the security services to counter this growing threat.

"It is vital that community voices are raised effectively to provide an alternative narrative to that of the recruitment agents for terrorism. That means ensuring that community members take the lead so that we can stem the flow of those who wish to go abroad to fight. We must act now.

"We also need to build an international platform through Interpol to ensure that we have an international approach to this issue."

Additional reporting from PA