James Foley knew his job carried risks but "believed in what he was doing" covering the Syrian conflict, a friend said.

The 40-year-old New Englander had been kidnapped before while covering fighting in Libya, but had been eager to get back into action, film-maker Matthew VanDyke told BBC Radio 4's Today programme.

He said seeing news reports of his friend's death was "a complete nightmare" and urged other reporters in Syria and Iraq to take precautions, saying "if it can happen to him, it can happen to anybody".

He said: "He was certainly aware of the dangers, he was very professional.

"He had been through a rough time in Libya when he was captured and even after that he came home a little bit and then he went right back to Libya to continue reporting on that conflict.

"And he went to Syria too knowing the dangers."

Mr VanDyke continued: "He had a love for what he did and he wanted to tell the story of the Syrian people. And nothing was going to stop him from doing that."

Mr Foley was kidnapped in northern Syria in 2012 when his car was stopped by militants while he was on an assignment for Agence France-Presse and the Boston-based media company GlobalPost.

The freelancer from Rochester, New Hampshire, has not been heard from since. He is one of an estimated 20 journalists missing in Syria, according to the New York-based Committee to Protect Journalists.

The beheading, if confirmed, will be the first time Islamic State fighters have killed an American since the conflict broke out in Syria in 2011.

Mr VanDyke added that IS did not even exist when Foley was captured in Syria in 2012. He had been told that the photojournalist was originally captured by members of Jabhat al Nusra, members of which subsequently joined the self-proclaimed caliphate.

After being captured in Libya, he was held by the government alongside a small group of other journalists, but was released and given a one-year suspended sentence on charges of illegally entering the country.

In an interview with the Associated Press about that experience, he said he "would love to go back", but recalled the tragedy of seeing a colleague killed in a firefight.

He also spoke of a love of his profession.

"Journalism is journalism," he said. "If I had a choice to do Nashua (New Hampshire) zoning meetings or give up journalism, I'll do it. I love writing and reporting."

He told the BBC in a 2012 interview that he was "drawn to the drama of the conflict and trying to expose untold stories".

He said: "There's extreme violence, but there's a will to find who these people really are. And I think that's what's really inspiring about it."

Philip Balboni, chief executive of GlobalPost, paid tribute to their employee, and thanked the public on behalf of Mr Foley's parents.

"On behalf of John and Diane Foley, and also GlobalPost, we deeply appreciate all of the messages of sympathy and support that have poured in since the news of Jim's possible execution first broke.

"We have been informed that the FBI is in the process of evaluating the video posted by the Islamic State to determine if it is authentic. ... We ask for your prayers for Jim and his family."