The charity that sent Scots hostage David Haines to Syria has called for his release.

Paris-based Acted condemned threats by terror group Islamic State to behead aid worker Mr Haines as intolerable and praised his long-standing humanitarian efforts.

The organisation posted Mr Haines, 44, to a refugee camp just inside the Syrian border in March 2013 but lost contact with him after he and his Italian colleague Federico Motka were seized by a gang.

Mr Motka was released months later amid reports the Italian government had paid a ransom.

Mr Haines was next seen on video this week, in an orange jump suit kneeling below a masked English-speaking militant who had just decapitated American journalist Steven Sotloff.

A communiqué by Acted said: "We are deeply shocked by the images broadcasted earlier this week. The threats on David Haines's life are intolerable.

"David has been working as a humanitarian since 1999, helping victims of conflict in the Balkans, Africa and the Middle East. When he was taken hostage in March 2013, David was in Syria as part of Acted's humanitarian effort in support of tens of thousands of people affected by the crisis.

"We have been mobilised from day one with David's family. More than ever, we are pursuing our efforts, and our thoughts are with David and his family."

It is understood Mr Haines was passed on by the gang to Islamic State, where he shared a cell with Mr Sotloff, a Jew who had to conceal his faith, and another American Journalist, James Foley, who was beheaded earlier. Both Americans were killed by a man with a British accent dubbed "Jihadi John".

Yesterday fears were expressed that Mr Haines, who was born in England but brought up in Scotland, had been tortured during the early part of his captivity. He had spent some time held with French journalists who were also subsequently released. Mr Motka, meanwhile, has never spoken of his ordeal.

Mr Haines's wife, Dragana, yesterday broke her silence at the family home near Zagreb, Croatia. Mr Haines, a former military expert, had worked for years in the former Yugoslavia. Mrs Haines, who has a child with Mr Haines, said: "He's everything to us. He's our life. He's a fantastic man and father.

"Nobody can understand how we are feeling. My daughter keeps asking about him every day. She hasn't seen her father for a year- and-a-half. She has gone through so much. She sees me crying all the time.

"My daughter was on a play date and I had to bring her home when I got the news.

"I just can't digest it right now. We just don't want to do anything to endanger his life."

The couple, who met when Mrs Haines worked as Mr Haines's translator, have a business selling catering equipment in the Balkans. Mr Haines spent years working with aid organisations, such as Acted and Nonviolent Peaceforce, in trouble spots as far apart as Libya and South Sudan.

While in the former Yugoslavia he helped many Muslims, said his former landlady, Nena Skoric, in the town of Petrinja, Croatia. "It didn't matter to him whether people were Croats, Serbs or Muslims, as long as they needed help," she said. "I don't know what is wrong with the kidnappers. Don't they know he was helping Muslims? They don't seem to care about that."

Mrs Skoric, 67, did not know that Mr Haines had been captured until she saw him on television. She said: "It was a terrible shock. I have been crying for two days since I found out what happened to him," she said."I thought 'not David, please not my David'. The whole town of Petrinja is shocked. People cannot believe it is true. We were hoping it must be someone else.

"Last night I woke up with the image of him kneeling in the desert wearing that orange suit. I can't get that picture out of my mind."

The grandmother had been worried that she had not heard from Mr Haines, who had regularly kept her up to date with what he did. Mr Haines, who went to Perth Academy, also has family and friends in Scotland.

They have suffered in silence, terrified of harming his chances of release, as Scottish - but not international media - observed a media blackout on his identity. His brother Michael yesterday thanked media for their understanding.

His 17-year-old daughter on a social media site said wrote: "What I want most is to have my dad home for good."