By Phil Stewart and Mariam Karouny
WASHINGTON/BEIRUT (Reuters) - The United States announced on Friday it was "reasonably certain" a drone strike in Syria had killed Jihadi John, a British citizen who became the public face of Islamic State and a symbol of its brutality after appearing in hostage execution videos.
U.S. and British officials welcomed the apparent success of the operation targeting Mohammed Emwazi, saying his death, if confirmed, would be a big blow to Islamic State's image and prestige even though Emwazi was not a significant tactical or operational figure in the militant group.
"If this strike was successful - and we still await confirmation of that - it will be a strike at the heart of ISIL (Islamic State)," British Prime Minister David Cameron said in a statement outside his official London residence.
The U.S.-British missile strike believed to have killed Emwazi was months in preparation but came together at lightning speed shortly before midnight on Thursday, as two U.S. MQ-9 Reaper drones and one British MQ-9 cruised above the Syrian town of Raqqa, officials said.
U.S. Army Colonel Steve Warren, a spokesman in Baghdad for the U.S.-led coalition against Islamic State, said a Hellfire missile was fired at a car believed to be carrying Emwazi and another man. The missile killed the people riding in the car, he said.
"It's still a little early, but we are reasonably certain that we killed the target that we intended to kill, which is Jihadi John," Warren told reporters, adding the verification process still had to be completed.
An Islamic State fighter confirmed a strike took place in Raqqa, the organization's headquarters in Syria, and killed several "brothers" and civilians but added via the Internet that "there is a decision not to announce names."
Rami Abdulrahman, director of the Syrian Observatory for Human Rights, a monitoring group, said a car carrying four Islamic State leaders, including one Briton, had been killed in the strike in Raqqa. He quoted sources in Raqqa as saying Emwazi's body had been blown apart.
While experts questioned whether Emwazi's death would have much impact on Islamic State since he was not a senior military figure, Cameron described him as a "barbaric murderer" and Islamic State's "lead executioner."
"It was the right thing to do," Cameron said.
Emwazi took part in videos showing the murders of U.S. journalists Steven Sotloff and James Foley, U.S. aid worker Abdul-Rahman Kassig, British aid workers David Haines and Alan Henning, Japanese journalist Kenji Goto, and other hostages.
Shown in the videos dressed entirely in black, a balaclava covering all but his eyes and the bridge of his nose, Emwazi became a menacing symbol of Islamic State brutality and one of the world's most wanted men.
He used such videos to threaten the West, admonish its Arab allies and taunt U.S. President Barack Obama and Cameron before hostages seen cowering in orange jump suits.
Born in Kuwait in 1988, Emwazi was brought to Britain by his family when he was 6 years old and graduated in computer programing in London.
He appears to have come to the attention of the British authorities police by 2009, when he was barred from entering Tanzania at the request of British security services.
The British government also believes Emwazi was a member of a network convicted of trying to bomb London's underground railway in 2005, two weeks after an attack by another group killed 52 people.
White House spokesman Josh Earnest told reporters the operation against Emwazi did not require prior presidential approval because it was conducted under guidance Obama laid down for the fight against Islamic State, which includes going after their leaders. He said Obama was briefed on the operation on Thursday.
The strike came as the U.S. president is trying to boost U.S. efforts to defeat Islamic State, including sending a small contingent of U.S. special forces troops to Syria.
RELIEF MIXED WITH FRESH GRIEF
Reacting to news about Emwazi, relatives of slain hostages spoke of relief but also a desire to hear him explain his actions.
"As much as I wanted him dead, I also wanted answers as to why he did it, why my Dad, how did it make a difference," said Bethany Haines, whose father David was shown being killed on video, told Britain's ITV News.
Steven Sotloff's parents, Art and Shirley Sotloff, said in a statement the development was "too little, too late" and they were focused on the positive contributions of their son and James Foley.
John and Diane Foley, parents of James, said in a statement: "If only so much effort had been given to finding and rescuing Jim and the other hostages who were subsequently murdered ... they might be alive today."
Experts said Emwazi's death may not make much difference to Islamic State or to the struggle against radicalization among some young British Muslims.
"Islamic State will survive 'Jihadi John'," said Jonathan Russell, political liaison officer at the Quilliam Foundation, which aims to debunk the belief systems of Islamic extremism.
"If we're going to make any sort of progress on winning this global war against Jihadism, we've got to focus on the ideology and win the battle of ideas, not just have a look at their propaganda tools and their frontmen and their symbols."
Peter Neumann, director of the International Centre for the Study of Radicalisation at King's College London, said the military impact would be small even if the symbolic importance was significant.
"It feeds into a wider narrative that ISIS (Islamic State) in its core territory isn't really winning anymore," he said.
(Additional reporting by John Davison in Beirut, Doina Chiacu in Washington, Estelle Shirbon in London and Robert Muller in Prague; Editing by Samia Nakhoul, Timothy Heritage, David Alexander and Frances Kerry)