By Jesse Byrnes - 08/29/14 11:09 AM EDT
The United Kingdom on Friday raised its terror threat level to “severe” amid growing concern over the dangers posed by fighters from the Islamic State in Iraq and Syria.
British Prime Minister David Cameron condemned ISIS as he announced the decision and vowed that the U.K. would not ignore threats to its homeland.
"The root cause of this threat to our security is quite clear: it is a poisonous ideology of Islamist extremism that is condemned by all faiths and by all faith leaders," Cameron added.
The “severe” threat level is the second-highest on the scale, above “substantial” but below “critical,” which designates a situation where an attack is imminently expected. The U.K. is now at its highest alert in three years.
Cameron said the decision was made by the U.K.'s joint terrorism analysis center.
The British leader called for a "comprehensive approach" to combating the Islamic extremists who have taken over large swaths of Iraq and Syria in recent months. Fears have also grown that fighters with the group who have Western passports could return to attack their home countries.
At least 500 British citizens had gone to Syria and potentially Iraq to fight with Islamic militants, Cameron said. He also noted the brutal murder of American journalist James Foley, reportedly at the hands of a British ISIS fighter.
Cameron’s announcement comes one day after President Obama faced criticism for his approach to ISIS.
During a White House briefing Thursday evening, Obama said “we don’t have a strategy yet.”
Administration officials were quick to jump into damage-control mode, with press secretary Josh Earnest insisting that Obama was only referring "to military options for striking" ISIS.
"Those options are still being developed by the Pentagon," Earnest said.
Obama has authorized strikes on ISIS in Iraq but is weighing whether to expand those operations to hit the group’s foothold in Syria.