British survivors returning from the Algerian gas plant hostage crisis have told of their experiences, with the mother of one saying that her son will have nightmares for life.

One Briton has been confirmed killed in the attack by Islamist militants, while a further five British nationals and one UK resident are either dead or unaccounted for.

Stephen McFaul, a 36-year-old electrician supervisor from Belfast, was among those who survived and has returned to his family.

Forced to wear explosives, he fled when the kidnappers' convoy he was in came under fire.

"He'll have nightmares for the rest of his life after the things he saw," his mother Marie told the Sunday Mirror.

"I don't think it's sunk in for him yet. It's so traumatic for him... he's spoken about it to me.

"He doesn't want to say anything publicly because he has friends still out there and he's so worried about them. He just wants to spend time with his family."

Fellow survivor Iain Strachan, 38, from Howwood outside Glasgow, told the tabloid: "I am fine but I don't want to say too much at the moment until we find out what has happened to the others."

Meanwhile the family of Darren Matthews said in a brief statement through the Foreign Office that they were relieved he had survived.

"We have been extremely worried about Darren and we are pleased and relieved to learn that he is safe and well. We look forward to having him home soon," they said.

An aircraft had been sent to Algeria to bring Britons back from the remote In Amenas plant near the Libyan border.

The dramatic four-day crisis ended in a bloodbath Saturday when Islamists executed all seven of their remaining foreign captives as Algerian troops stormed the desert complex.

Relatives of Kenneth Whiteside, 59, an engineer from Glenrothes in Scotland, were left "devastated" after hearing that an Algerian co-worker claimed to have witnessed him being shot but dying bravely with a smile on his face.

Whiteside's brother Robert, 66, told The Mail on Sunday newspaper: "It is now just a waiting game and we are suffering badly.

"We are trying to keep a lid on our anger at the lack of information but it is almost more than we can bear at times. The latest report from one of his colleagues has left us devastated."

His wife Stephanie added: "We've had no official confirmation about Kenny. But why would his Algerian co-worker say something like that, knowing the upset that it would cause to his family if it wasn't true?"

Scotland's First Minister Alex Salmond said: "We now face the difficult news that there are Scots or individuals with strong Scottish connections among those who are believed to have been killed or remain unaccounted for.

"Two families have been informed of the position.

"We will provide details as soon as we are satisfied that the information is full and final.

"The Scottish authorities continue to offer every support to all caught up in this crisis.

"We extend our condolences to all those, of all nationalities, who have lost loved ones and colleagues in this terrorist outrage."