File photo of Alan Henning, the British hostage beheaded by Islamic State jihadists. (Associated Press)
Families of two British aid workers killed by the Islamic State group in Syria on Saturday urged people of all faiths to unite against the militants' "hateful acts."
In a letter published in the Guardian newspaper, Barbara Henning and Michael Haines urged everyone "to find a single act of unity - one simple gesture, one act, one moment that draws people together."
They said that "we will not allow the actions of a few people to undermine the unity of people of all faiths in our society.Together we have the power to defeat the most hateful acts."
Barbara Henning's husband Alan and Michael Haines' brother, David are two of the Western hostages beheaded on IS propaganda videos.
A memorial service is being held for Haines on Saturday in his hometown of Perth, Scotland. The 44-year old former air force engineer was working for the ACTED agency helping refugees from the Syrian civil war when he was abducted in March 2013 near the Turkish border.
In a video message released before the service, Michael Haines remembered his brother as "a man full of kindness, open and caring, willing to cross the road to help others."
The militants have also killed US reporter James Foley and American-Israeli journalist Steven Sotloff, and threatened another American, Abdul-Rahman Kassig. The group also holds British photojournalist John Cantlie.