“That means that a terrorist attack is highly likely, but there is no intelligence to suggest that an attack is imminent,” Home Secretary Theresa May said.
The U.S. Department of Homeland Security, meanwhile, said it is not aware of any specific, credible threat to the United States.
British Prime Minister David Cameron said the “root cause” of the terrorist threat in the United Kingdom is “Islamist extremism.” He said the recent killing of U.S. journalist James Foley is clear evidence that ISIS’s fight in Iraq and Syria “is not some foreign conflict thousands of miles from home that we can hope to ignore.”
The danger that ISIS poses now is a “greater and deeper” threat to the UK’s security than the country has ever known, Cameron said.
This is in part because ISIS is not simply seeking refuge in a country but ruthlessly seeking its own terrorist state and expanding, he said.
Cameron said he will soon announce plans to stop would-be jihadists from traveling to Syria and Iraq and to make it easier to take their passports away.
Britain also needs to do more to stop current fighters from returning from the Middle East and to deal decisively with those who already have returned, he said.
UK authorities estimate that 500 Britons have gone to Syria and Iraq to fight with Islamist groups.
The Prime Minister warned against having a knee-jerk response to the threat and said a number of tools must be deployed, the military being just one of them.
An intelligent response will involve aid, diplomacy and political influence, too, he said.
A distinction must be made between the religion of Islam and the “poisonous” political ideology of Islamic extremists, he said.
The UK has five levels of terror threat. It had been at “substantial” since July 11, 2011. The level is set by the Joint Terrorism Analysis Center and the Security Service.
The United States had a color-coded scale that was discontinued in 2011. The system that replaced it, the National Terrorism Advisory System, sends out alerts on its website and to the media when there is an elevated threat.
As the U.S. Labor Day holiday nears, Ross Feinstein, Transportation Security Administration press secretary, says that the terror threat level has not changed for the TSA and that it is customary to see increased security presence leading up to a holiday weekend.
Feinstein stressed that he is speaking for the TSA and not the overall terror threat level, which is not determined by his agency.
U.S. Secretary of Homeland Security Jeh Johnson said that although there is no specific threat against the United States, ISIS has proved to be a threat to Americans overseas.
His department “has taken a number of steps to enhance aviation security at overseas airports with direct flights to the United States, and the United Kingdom and other nations have followed with similar enhancements.”
Britain’s national policing lead for counterterrorism, Mark Rowley, said police activity relating to the jihadist threat has escalated for months.
“The ongoing commitment to fight this threat has seen a significant rise in the number of Syria-related arrests,” he said in a statement. “The first half of this year has seen a total of 69 arrests made for a variety of offenses, including fundraising for terrorist activity through to the preparation and/or instigation of terrorism acts and traveling abroad for terrorist training.”
The U.S. military conducted airstrikes Friday against ISIS fighters near Iraq’s Mosul Dam, according to U.S. Central Command.
The strikes destroyed four armored vehicles, damaged one more and destroyed three support vehicles, all belonging to the terrorist group, the military said.
The U.S. has carried out 110 airstrikes in Iraq since August 8.
The cost of the airstrikes has varied as they have intensified, but Pentagon spokesman Rear Adm. John Kirby said that on average, it is costing $7.5 million per day. The money comes from the Overseas Contingency Operations Fund for 2014, and “we’re well within our limits in that regard,” he said.
Kirby, like the British Prime Minister, argued that military action alone is not enough to combat extremism.
“If we’ve learned nothing over 13 years of war, it’s that you can’t completely eliminate extremism anywhere through simply kinetics, through airstrikes alone,” he said at a press briefing Friday.