WASHINGTON — The United States is not aware of any specific threat to the U.S. homeland from Islamic State militants, the Department of Homeland Security said on Friday after Britain raised its international terrorism threat level.
Islamic State militants and their supporters, however, “have demonstrated the intent and capability to target American citizens overseas,” Homeland Security Secretary Jeh Johnson said in a statement. He noted that DHS took steps over the summer to strengthen security at overseas airports with direct flights to the United States.
Johnson said he has spoken to U.K. Home Secretary Theresa May about Britain’s decision to raise its terrorism alert to the second-highest level. It is the first time since mid-2011 that Britain has been placed on an alert level this high.
U.K. Prime Minister David Cameron said the threat to Britain from Islamic State militants is greater than anything previously faced, as the government raised the terror threat level to “severe,” the second-highest level, based on new intelligence.
Cameron told reporters that the public could expect to see more police, including armed officers, on the streets as a result of the increased threat level. He will also announce new legislation on Monday to make it easier to confiscate the passports of people who are suspected of wanting to travel to join extremist groups.
Speaking in London on Friday, Cameron said the battle against Islamic extremism is a “generational struggle” which will probably last decades. He said Islamic State, the Sunni militant group also known as ISIL and ISIS that has captured ground in both Syria and Iraq, had taken it to a new level.
“What we are facing in Iraq now with ISIL is a greater threat to our security than we have seen before,” the prime minister said. “We could be facing a terrorist state on the shores of the Mediterranean and bordering a NATO member.”
North Atlantic Treaty Organization member Turkey shares a border with both Syria and Iraq.
Britain’s “severe” terrorism threat rating means an attack is “highly likely” but no intelligence exists about a specific plot. The highest level is “imminent.”
Cameron said Islamic State “believes in using the most brutal forms of terrorism to force people to accept a warped world view and live in an almost medieval state.”
He said that military force was only part of fighting IS, and that political change would be needed in the region as well.
Earlier, Home Secretary May explained the decision by the government’s the Joint Terrorism Analysis Center to raise the threat level.
May said on Friday that Britain increased its threat level because militant groups in Syria in Iraq were “planning attacks against the West” and some attack plots were “likely” to involve foreign fighters from Britain and elsewhere in western Europe.
However, U.K. authorities also have said they have no knowledge of any “imminent” plot to attack British targets.
U.S. and European officials have said that because of relaxed border controls between European Union countries, it is difficult to track travel to Syria and Iraq by would-be foreign fighters. Often suspected militants are not identified until after they return to their home countries.
U.S. authorities are particularly concerned about former foreign fighters in Syria and Iraq who have British or other European passports that would allow them to enter the United States with instant visas and minimal security vetting.
U.S. and European officials have estimated that as many as 100 Americans have traveled to Syria or Iraq to fight with militants, along with four or five times as many Britons and hundreds of other Western Europeans.
“This is a threat that the United States has been focused on. We’ve been coordinating closely with our allies, both the Brits, but others in Europe, about countering this threat and mitigating it,” White House spokesman Josh Earnest said at a news briefing.
There was no plan to raise the U.S. threat assessment level, he said.
While the United States once characterized threats under a system of color coded warnings, the Obama administration abandoned that system and now issues warnings targeted to particular transport or economic sectors.
Cameron said at least 500 people have traveled from Britain to fight in Iraq and Syria with IS.
Bloomberg and Reuters contributed to this report