Media playback is unsupported on your device Media caption The masked militant first appeared in numerous gruesome videos put out by Islamic State, as Lucy Manning reports

The widow of a man killed by a masked Islamic State militant known as "Jihadi John" says she wants him caught alive.

Dragana Haines said the "last thing" she wanted for the man who had killed her husband, British aid worker David Haines, was an "honourable death".

The militant, pictured in the videos of the beheadings of Western hostages, has been named as Mohammed Emwazi, a Kuwaiti-born Briton from west London.

Mr Haines' daughter said she wanted to see "a bullet between his eyes".

Emwazi, who is in his mid-20s and was previously known to British security services, first appeared in a video last August, when he apparently killed the US journalist James Foley.

Media playback is unsupported on your device Media caption Dragana Haines, wife of slain hostage David: "I hope he will be caught alive... He needs to be put to justice"

He was later thought to have been pictured in the videos of the beheadings of Mr Haines, US journalist Steven Sotloff, British taxi driver Alan Henning, and American aid worker Abdul-Rahman Kassig, also known as Peter.

Mrs Haines told the BBC she wanted him to be caught alive and not have an "honourable death" by being killed in action.

She added: "I think he needs to be put to justice, but not in that way."

However Mr Haines' daughter, Bethany, told ITV News: "I think all the families will feel closure and relief once there's a bullet between his eyes."

Image copyright Family handouts Image caption (Clockwise from left) Islamic State foreign victims James Foley, Abdul-Rahman (Peter) Kassig, Alan Henning, Kenji Goto and Steven Sotloff

There have been questions about how Emwazi was able to travel to Syria and how he may have been radicalised.

Emwazi graduated from the University of Westminster in 2009 and it has been suggested he may have come into contact with extremists while he was a student there.

Student Rights, a group tackling extremism on university campuses, told BBC News it had found a number of events at the university that featured extremist Islamist preachers, and large amounts of extremist material had been shared with students.

Rupert Sutton, the group's director, said: "Given that he travelled so soon after graduating, it's entirely possible he picked up the views that led him to travel whilst he was studying."

As a mum I forgive him Diane Foley, Mother of IS murder victim James Foley

A spokesman from the University of Westminster said it "condemned the promotion of radicalisation, terrorism and violence or threats against any member of our community".

It said the Education Act placed two competing responsibilities on universities to promote free speech and a duty to protect students from harm, but it was working with the government's Prevent strategy to tackle extremism.

BBC security correspondent Frank Gardner told Radio 4's Today programme there were questions for the security services about how "someone on a terror watch list, somebody of real concern, was able to slip out of this country and turn up in Syria like that unhindered".

While Chris Phillips, former head of the National Counter Terrorism Security Office, said the case demonstrated the need for security services to have increased powers, including access to phone records, proposed in the so-called "snoopers' charter".

He said: "It's clear also that TPIMs (Terrorism Prevention and Investigation Measures) and control orders just don't work. We need to have a way of dealing with people in this kind of situation.

"The numbers are growing and the police resources are not."

Analysis: Frank Gardner, BBC News

US and British counter-terrorism officials discovered the identity of "Jihadi John" as far back as last September. The FBI, Britain's MI5 and other intelligence agencies used a combination of voice-recognition software, interviews with former hostages and on-the-ground research in London to build up a profile of the man now revealed to be Mohammed Emwazi.

They have always declined to reveal the name for "operational reasons". Now that it's out in the public domain, it's emerged that Emwazi was well known to MI5 and that it even tried to recruit him as an informer, years before he went off to Syria to eventually join Islamic State.

The practice by intelligence agencies of approaching jihadist sympathisers to work for them is likely to continue. It's believed both Britain and the US have informers inside the Islamic State "capital" of Raqqa. Yet this seems to have been little help in stopping the actions of Mohammed Emwazi, or bringing him to justice.

Profile: Mohammed Emwazi

Jihadist's 'typical trajectory'

Dr Afzal Ashraf, a counter-terrorism and counter-insurgency expert who advised the government on the Prevent strategy between 2009 and 2011, said people were more likely to be radicalised by groups they believed could be successful.

"One of the reasons we don't have Nazis and right-wing extremists in great numbers doing what they do is because Nazism and right-wing extremism has been discredited.

"Not many people believe they are going to change the world into that format.

"The problem is that al-Qaeda, and now IS, has demonstrated a degree of success as far as these people are concerned and they actually believe there is a possibility of success."

These people are inhumane dogs Kasim Jameel, Friend of IS murder victim Alan Henning

In each of the videos Emwazi appeared in, the militant was dressed in a black robe with a black balaclava covering all but his eyes and top of his nose.

Speaking with a British accent, he taunted Western powers before holding his knife to the hostages' necks, appearing to start cutting before the film stopped. The victims' decapitated bodies were then shown.

Earlier this month, a video in which the Japanese journalist Kenji Goto appeared to be beheaded featured the militant.

Hostages released by IS said he was one of three British jihadists guarding Westerners abducted by the group in Syria. They were known collectively as "the Beatles".

A spokesman for the family of Steven Sotloff said: "We want to sit in a courtroom, watch him sentenced and see him sent to a super-max prison."

Mr Foley's mother Diane told the Times that she forgave her son's killer.

"It saddens me, [Emwazi's] continued hatred," she said. "He felt wronged, now we hate him - now that just prolongs the hatred. We need to end it.

"As a mum I forgive him. You know, the whole thing is tragic - an ongoing tragedy."

Kasim Jameel, a friend of Mr Henning, told The Times he wanted Emwazi dead.

Mr Jameel, who led an aid convoy that was joined by Mr Henning, said: "He needs to be annihilated. I wouldn't believe in an eye for an eye but he murdered my best friend and he should be eradicated."

He added: "These people are inhumane dogs, they are worse than any other terrorist group and I don't care how he's killed, whether it's by the security services or a US drone, it might finally bring some closure."

Mohammed Emwazi's movements before heading to Syria

1. Aug 2009, refused entry to Tanzania: travels to Tanzania with two friends, but is refused entry at Dar es Salaam. Tanzanian police have denied Emwazi's name is on their database of suspected foreign criminals detained and deported in 2009, as he had claimed. Emwazi and his friends are put on flight to Amsterdam, where they are questioned. They return to Dover and are questioned again.

travels to Tanzania with two friends, but is refused entry at Dar es Salaam. Tanzanian police have denied Emwazi's name is on their database of suspected foreign criminals detained and deported in 2009, as he had claimed. Emwazi and his friends are put on flight to Amsterdam, where they are questioned. They return to Dover and are questioned again. 2. Sept 2009, travels to Kuwait for work: leaves the UK for Kuwait for work.

leaves the UK for Kuwait for work. 3. May/June 2010, returns to UK for holiday: he returns to the UK for an eight-day visit.

he returns to the UK for an eight-day visit. 4. July 2010, refused re-entry to Kuwait: Emwazi returns to the UK once more for a couple of days. He is stopped at Heathrow on his return to Kuwait and told he cannot travel as his visa has expired.

Emwazi returns to the UK once more for a couple of days. He is stopped at Heathrow on his return to Kuwait and told he cannot travel as his visa has expired. 5. 2013, travels to Syria: Emwazi changes his name to Mohammed al-Ayan and attempts to travel to Kuwait but is stopped and questioned. Three days later, he heads abroad. Police later inform his family he has travelled to Syria.

Source: Cage

'Jihadi John' movement mapped

In a news conference on Thursday, Asim Qureshi, the research director of the London-based lobby group Cage, which had been in contact with Emwazi over a number of years, detailed the difficulties Emwazi had faced with security services in the UK and overseas.

Mr Qureshi said Emwazi, who is understood to be about 27, had been "extremely kind, gentle and soft-spoken, the most humble young person I knew".

But Cage was told by Emwazi that he was "harassed" by security services, with later emails suggesting he was "witnessing perceived injustices everywhere", Mr Qureshi said.

However, Rafaello Pantucci, author of We Love Life As You Love Death, said the suggestion the security services may have driven Emwazi to carry out his killings was "disproportionate".

He said: "Security services asking questions and making your life a little bit difficult and ending up murdering people in this very cold-blooded way seems a very disproportionate causal link."

Profile: Cage

Image copyright Nick Ansell Image caption Asim Qureshi of Cage, John Rees of Stop the War Coalition and Ceri Bullivant of Cage

Cage, formerly known as Cageprisoners, is an advocacy group set up by former Guantanamo detainee Moazzem Begg.

It describes itself as "an independent organisation working to empower communities impacted by the War on Terror".

Cage has spoken out against the UK's anti-terrorism laws, describing them as draconian and targeting Muslims.

Cage campaigned for the release of the Salford taxi driver Alan Henning, before he was murdered by Islamic State militants in Syria last October.

Cage has also worked with family of Michael Adebolajo, who was convicted of killing Fusilier Lee Rigby in Woolwich in 2013.

Emwazi 'claimed harassment'

According to Cage, Emwazi had travelled to Tanzania in May 2009 following his graduation in computer programming from the University of Westminster.

Mr Qureshi said Emwazi and two friends had planned to go on a safari but once they landed in Dar es Salaam they were detained by police and held overnight.

Tanzanian police appeared to contradict this account and said Mohammed Emwazi's name was not in their database of suspected foreign criminals detained and deported in 2009, though they said he might have been using another identity or forged travel

Emwazi then ended up flying to Amsterdam, in the Netherlands, where he claimed to be met by British intelligence agents from MI5 who accused him of trying to travel to Somalia, where the jihadist group al-Shabab operates. He denied the accusation and said the agents had tried to recruit him before allowing him to return to the UK.

In early 2013, at his father's suggestion, Emwazi changed his name by deed poll to Mohammed al-Ayan, Cage said.

Emwazi was believed to have travelled to Syria around 2013 and later joined IS, which has declared the creation of a "caliphate" in the large swathes of Syria and neighbouring Iraq it controls.

A spokeswoman for Prime Minister David Cameron would not confirm or deny the latest reports, adding that the police and security services were working hard to find those responsible for the murder of the British hostages.

British police have not commented on the identity of the militant known as "Jihadi John", citing ongoing inquiries.

Jihadi John sightings