Transcript for ISIS Calls for Civilian Murder
We begin with the newest call to action this evening. The direct threat from Isis. Many westerners who join their side. And an urgent hunt for any American that may be thinking of joining the group. We begin with Brian Ross. What are you learning? Reporter: The three cities, that's where they're going to start. Confronting the threat from Isis is now the highest urgency. Reporter: As Isis turned up the tempo of its propoganda machine today, with new videos of its military-like formations, and dire threats to American civilians. U.s. Officials revealed details of a promised crackdown on westerners who want to join Isis or already have, like these Britons appearing in a new video today. We are working very closely with our international partners to try and mitigate this threat -- to keep eyes on these individuals and to monitor their movements. Reporter: U.s. Officials said efforts to shut down the jihad pipeline to Isis will focus on Boston, Minneapolis and Los Angeles. Cities that have already sent a number of young recruits, men and women for the terror group. The urgency of the coming white house push against Isis was underscored today by one of the terror group's weekend propaganda messages. Its chief spokesperson urged supporters around the world, "If you can kill a disbelieving American or european, especially the spiteful and filthy French, or an Australian, or a Canadian, then rely upon Allah, and kill him in any manner or way -- however it may be." Today, Isis followers in Algeria posted this video of a man who they will behead in 24 hours. And three -- never a threat to the U.S. And I want to bring in Martha Raddatz tonight. As you know, the images pouring in. More than 100,000 families in danger. Well, the attacks have been relentless. Using tanks and artillery. 100,000 streaming across the border into Turkey. It points to the urgency of the problem. The U.S. Has been targeting places in Iraq, and also considering strikes in Syria as well. The U.S. Has been picking targets for weeks. Including weapons, convoys, and any training area. And the president will be at the U.N. This week trying to get support.
This transcript has been automatically generated and may not be 100% accurate.