THREATS to kill an aid worker who travelled to Syria with a Bolton convoy have added fresh urgency to efforts to form an international coalition to mount an assault on Islamic State (IS) extremists.

Foreign Secretary Philip Hammond will attend a summit in Paris as the USA seeks military commitments from allies for the fight to push back the jihadist advance.

The threats to kill 47-year-old former cabbie Alan Henning were made at the end of a video released on Saturday, showing the brutal murder of British aid worker David Haines.

Downing Street has ruled out any immediate recall of Parliament but former military chiefs are among those pressing for the UK to join air strikes.

Prime Minister David Cameron said the UK would seek to "mobilise the broadest possible support to bear down" on IS at the United Nations as efforts continue to form a coalition of countries – especially those in the region – to take part in a concerted offensive.

He said: "This is not about British combat troops on the ground, it is about working with others to extinguish this terrorist threat. As this strategy intensifies we are ready to take whatever steps are necessary to deal with this threat and keep our country safe."

Mr Henning travelled from Bolton to Syria in December last year with eight other volunteers from Bolton alongside the UK Arab Society.

Bolton aid worker and fellow volunteer Kasim Jameel, who travelled to Syria with Mr Henning, said: "Alan is an amazing guy. He is the best of the best. He is my best friend and I am praying for him.

"He loved the cause so much that when he went to Turkey on holiday with his family, he had a big tattoo across his arm saying ‘aid for Syria’ — he was that dedicated.

"The cause had literally changed his life around — it meant that much to him."

Mr Henning was described as "passionate" volunteer who "took that extra risk" to deliver aid.

He has helped on at least two convoys into Syria, where humanitarian volunteers drive supplies across the Turkish border into the war-torn country.

He helped load supplies into ambulances that were to be driven to Syria to help refugees.

His friend Mohamed Elhaddad, company director of the UK Arabic Society, has spoken of Mr Henning's determination to help others.

Mr Elhaddad, British convoy leader, described the hostage as a passionate humanitarian volunteer, but said he insisted on going a long way into Syria to deliver aid.

Mr Elhaddad said: "I remember going on two convoys with him, at the end of 2012 and in May 2013, and 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."

Mr Henning, from Eccles, has been described as very likeable. Colleagues nicknamed him “Gadget” and also praised his sense of humour.