There must be a "global response" to the "global threat" posed by Islamic State (IS) extremists, French president Francois Hollande has said.
Speaking at the start of a conference in Paris aimed at coordinating a strategy against IS, Hollande said: "What is the threat? It is global so the response must be global."
Islamic State (IS) have "hijacked the name of Islam", according to a Shia sheikh, who is campaigning for the media and public to change the name they use for the terrorist group.
Sheikh Mohammed Al-Hilli told Good Morning Britain: "The goal is to get them to understand that this is nothing to do with Islam what so ever. It's barbaric and it's against humanity."
French aircraft will carry out their first surveillance missions in Iraq today, France's foreign minister said.
It comes as international diplomats prepare to meet in Paris to discuss ways to tackle Islamic State militants following the murder of a British aid worker.
Kidnappings by Islamic State (IS) are better thought of as "a slow motion murder," as they are carried out to terrorise any would-be enemies, a hostage negotiator has warned.
Dr James Alvarez told Good Morning Britain: "They have hold these hostages for a long time, and then trotted them out when they are ready and have done the unspeakable things they have done."
Washington said countries in the Middle East had offered to join air strikes against Islamic State militants and Australia said it would send troops, but Britain held back even after the group beheaded a British hostage and threatened to kill another.
US Secretary of State John Kerry has been touring the Middle East to try to secure backing for US efforts to build a coalition to fight the Islamic State militants who have grabbed territory in Syria and Iraq.
"We have countries in this region, countries outside of this region, in addition to the United States, all of whom are prepared to engage in military assistance, in actual strikes if that is what it requires," Mr Kerry said.
"And we also have a growing number of people who are prepared to do all the other things," he said in remarks broadcast on the CBS programme Face the Nation.
Britain would be "mad" not to deploy its military prowess to tackle Islamic State, London Mayor Boris Johnson said. Writing in the Daily Telegraph, Mr Johnson said:
For all our occasional spasms of self-doubt, we are one of the great powers of the world with some of the finest armed forces. We would be mad not to use our defence capability, where we can, to make the world a better place.
The brutal murder of one British aid worker and threat to kill a second will add urgency to efforts today to form a substantial international coalition to mount an assault on Islamic State (IS) extremists.
Foreign Secretary Philip Hammond will attend a summit in Paris as Washington seeks military commitments from more regional and global allies for the fight to push back the jihadist advance.
British hostage Alan Henning's life is in danger, simply because he volunteered to help those who were suffering in Syria, ITV News correspondent Juliet Bremner reports.
The deliberate targeting of aid workers by the Islamic State has made their job significantly more dangerous:
Alan Henning helped on at least two convoys into Syria, where humanitarian volunteers drive supplies across the Turkish border into the war-torn country.
His friend Mohamed Elhaddad, company director of the UK Arabic Society, said he insisted on going a long way into Syria to make sure the aid reached its intended recipients.
Mr Elhaddad said:
He was always very positive and very interested in the work.
I have met his family and his children. The first time we went together he was very excited and very emotional. He does a lot for others.
He is good at DIY and he was a useful person to have on the trips.
But Alan went too far into Syria. He took that extra risk, because he could have accomplished the drop-off at the border.
I disagree completely with what is happening to him. Alan is my friend, this is extremely sad for him and his family. It is a very sad situation.
Today's emergency meeting of the Government's Cobra committee did not produce a decision to respond militarily to David Haines' death.
The Government said a knee-jerk reaction would be allowing the militants to set the agenda.
Instead, they will continue the long-term strategy of destroying Islamic State (IS) as part of a coalition.
ITV News Political Correspondent Carl Dinnen reports: