WASHINGTON — FBI Director James Comey said Thursday he believes the bureau knows the identity of the masked executioner in ISIS propaganda videos. He declined to say who it is or where the man is from. In a question-and-answer session with reporters at bureau headquarters, he also said the FBI is working hard to identify two people in ISIS videos who appear to have American or Canadian accents.

“We have a big focus going on that right now,” Comey said. He said the FBI believes that ISIS is “looking to try to do something in the U.S.,” though he said he did not believe the group is capable of a sophisticated or complex attack.

The Khorasan terror group, an al Qaeda offshoot that was targeted along with ISIS by American airstrikes in Syria earlier this week, has “been at the top of my list of things to worry about” for months, Comey said. But he said: “We don’t have complete visibility about their activities. We believe they’ve been working toward an attack, but it’s hard to say whether it would come tomorrow, in three weeks, or in three months.”

Comey said he assumes the group still exists because he has not heard otherwise from the Pentagon. He said, “I have to assume they can still plot” until information proves otherwise.

IN-DEPTH

— Pete Williams