US forces are targeting the Islamic State executioner known as "Jihadi John".

The British raised university graduate Mohammed Emwazi was unmasked by media this week as the English-speaking executioner responsible for the beheading of at least five Western hostages held by the IS group in Syria and Iraq.

Asked whether the US was "going after" Emwazi specifically, Democratic Senator Dianne Feinstein responded affirmatively.

"Oh, yes. He's a target. There should be no question about that," the former Senate Intelligence Committee chair told CBS television's Face the Nation.

The Kuwait-born computer expert, believed to be 26 or 27-years-old, appeared for the first time in a video during the execution of American journalist James Foley in 2014.

He has presided over numerous killings and delivered English messages in execution videos.

Feinstein added that Emwazi's story illustrated a "major problem" for Western nations.

"What it tells us is that there are many young people and you can see this by the number of tweets on Twitter, who are so disaffected," she said.

"Whether they feel rejected socially, whether they feel they don't have an opportunity, whether they feel this country is anti-Muslim, which it is not, I don't know."