THE daughter of a hostage murdered by Islamic State terrorists has given her support to military action in Iraq as the US said it believes it has identified the British extremist in the video showing her father being beheaded.

Bethany Haines, 17, said the murder of her father David Haines, who grew up in Perth, had torn her family apart, but had also made them stronger. She spoke out ahead of a Commons vote today in which MPs are expected to back a call for British warplanes to join international airstrikes on the terror group.

The teenager, who praised Mr Haines as "amazing, brilliant", said she supported the use of UK war-planes to target the militants, adding: "IS need to be eradicated. They can't be doing this to people and getting away with it no matter what nationality, if they're Western or not. Hundreds of Syrians have been killed by them and they need to be stopped."

In the US, FBI director James Comey said he believed the man known as "Jihadi John" had been identified. He speaks with a British accent and is seen holding a knife in the videos showing the killings of Mr Haines and American reporters James Foley and Steven Sotloff.

Asked if he would prioritise capturing the jihadist, Mr Comey said: "We will do, and expend the effort that I think the American people would want us to and expect us to."

On the eve of today's vote, which could see the UK carry out airstrikes within days, the Defence Secretary, Michael Fallon, warned military involvement in Iraq could last for years. Mr Fallon said that UK Armed Forces would be in it for the long haul.

The motion before MPs will specifically prohibit action in nearby Syria, where IS also has strongholds.