WARNING: Video contains graphic images. CBN News's expert team discusses the contrast between the UK's response to the ISIS threat vs. that of the United States.
Authorities in London raised the terror level in the United Kingdom on Friday from "substantial" to "severe."
The move comes after Islamic State (ISIS) released video of some 150 Syrian soldiers, stripped to their underwear, being marched across the desert to their deaths - another mass execution.
Also, just last week ISIS displayed gruesome footage of the beheading of American journalist James Foley. The executioner in that video is believed to be a British national.
British officials cited such recent developments as the reason for raising the threat level.
"IS is a greater and deeper threat to our security than we have known before," British Prime Minister David Cameron said.
Islam: Religion of Peace or War?
Arabic scholars bring you a historical and shocking narrative on the tenets of Islam and the life of its founder.
Know the truth. Download now.
Cameron pledged to increase Britain's security, describing the extremist threat posed by ISIS as more dangerous than al Qaeda.
"We will respond calmly and with purpose," he vowed. "And we will do so driven by the evidence and the importance of maintaining the liberty that is the hallmark of the society that we defend. But we have to listen carefully to the security and intelligence officers who do so much every day to keep us safe."
Cameron's strong statement contrasted sharply with President Barack Obama's bizarre admission in a press conference Thursday that he didn't yet have a strategy in place on how to deal with the jihadist army.
"The suggestion seems to have been that we're about to go full-scale on an elaborate strategy for defeating ISIS," he told reporters. "I don't want to put the cart before the horse. We don't have a strategy -- yet."
The president's words come as both current and former U.S. intelligence officials said jihadi chatter has picked up among overseas terrorists organizations on phone lines and the Internet ahead of this year's 9/11 anniversary.
"This is certainly concerning, but as of yet we can't pinpoint what or if they are planning a particular attack," one U.S. government official told The Blaze.
The official said it's not clear if an attack is being planned. But he acknowledged there was a similar increase in chatter before 9/11. And some say terrorists from both al Qaeda and Islamic State (ISIS) may want to launch an attack.
Even so, Obama said he is still weighing the prospect of military action in Syria. But while the president tries to decide what to do, the terrorists of ISIS are not sitting still.
Even members of his own administration have been vocal about the need to move into the country. Democratic lawmakers are calling on the administration to take action as well.
Sen. Bill Nelson, D-Fla., just back from Turkey, said Thursday that the United States needs to have a military plan.
"Sooner or later we've got to take the fight to ISIS in addition to what we're doing in northern Iraq and protecting the Kurds in Kurdistan. Because sooner or later we're going to have to deal with them," he warned.
Nelson said the United States can avoid boots on the ground in Syria by cooperating with the Free Syria Army.
Earlier this month the president authorized limited air strikes against ISIS in Iraq. He initially seemed to rule out the option of extending the strikes into Syria where ISIS jihadists enjoy a safe haven.
The idea of staying out of Syria has now become more complicated, however after ISIS extremists announced the killing of Foley and threatened to kill more U.S. hostages in Syria.
Obama leaves next Tuesday for a trip to Estonia and a NATO summit in Wales. The crisis in Ukraine is expected to be a focus of discussion among NATO leaders.