MIAMI (AFP) - The family of Steven Sotloff, an American-Israeli journalist murdered by the Islamic State in Iraq and Syria, said they were relishing seeing his killer face justice after the apparent executioner was named on Thursday.

The masked militant dubbed "Jihadi John", believed to be responsible for beheading Western hostages, including Sotloff, was revealed by experts and the media to be Kuwaiti-born London computer programmer Mohammed Emwazi.

"The Sotloff family was informed of John's identity. This is one step on a long road to bringing him to justice," said Barak Barfi, the Sotloff family's spokesman, in a statement.

"If indeed Mohammed Emwazi is the man who executed Steve, the Sotloffs have full faith that the American intelligence community and law enforcement agencies will apprehend him.

"They look forward to the day that John will be prosecuted and convicted for the crime of executing Steve.

"That is how American justice is served and that is why this nation will prevail over the evil forces that seek to deny us our way of life."

"Jihadi John", named after Beatle John Lennon due to his British accent, is believed to be responsible for the murders of Sotloff and another US journalist James Foley, as well as British aid workers David Haines and Allan Henning, and American aid worker Abdul-Rahman Kassig.

He also appeared in a video with the Japanese hostages Haruna Yukawa and Kenji Goto, shortly before they were killed.