Heather Chitty has heard her son is safe

"I just thought 'Oh God' and then I thought of my little grandsons," said Heather Chitty from Cornwall.

She has since learnt her son, Warrant Officer Michael Chitty, is not among those kidnapped on Friday morning. "We fully believe he is safe," she said.

But she added she was "devastated" for the families of the abducted men, who have now all been informed.

" I know how it feels because I felt it initially until we knew Michael was OK," said Mrs Chitty.

"Although that gave us relief in one way it hasn't really because it is still so serious."

Meanwhile Devonport MP Alison Seabeck said it was "a very anxious time" and her thoughts were with the families.

Family information line 0845 7800 900

HMS Cornwall, a type-22 Frigate, left its home port of Devonport, Plymouth, on 22 January. There are 250 servicemen and women on board.

"I have no doubt that both the Foreign Office and the MoD will be doing all they can to ensure their release as soon as possible," said Ms Seabeck.

"It is very worrying for the individuals and their families, clearly if there is an error or they drifted into wrong waters by mistake an explanation will be given and hopefully the government in Tehran will accept that as being the case."

My immediate concern is that their safety and their safe return to me is ensured Commodore Nick Lambert UK soldiers captured at gunpoint

A helpline has been set up for families anxious for news of their loved ones.

HMS Cornwall's commanding officer, Commodore Nick Lambert, said "everything was being done at the highest level" to secure the men's release.

"My immediate concern is that their safety and their safe return to me is ensured.

"I can assure all of the families out there everything is being done at the highest level of the UK Government - and indeed of the coalition structure that we are working under - to ensure that safe return as soon as possible."

'Everyone responds differently'

The Bishop of Truro, Bill Ind, said he was thinking of the families who he said would be "finding it very hard".

"It is an awful thing where you discover something has happened and the result is that people are kidnapped and you don't know where they are and you don't know what they're doing, that's very hard." he said.

The type-22 frigate sailed from Plymouth via Falmouth

An MoD spokesman said the families of the kidnapped men had all been contacted and were being offered practical and emotional help and support.

The families are believed to live in various parts of the UK.

When an incident such as this happens a nominated family member is visited by Royal Navy staff who offer help and information.

"It is mostly emotional support which is offered and the Royal Navy only sends people who are professional, empathetic and sympathetic," said the MoD spokesman.

"Everyone responds differently and some might want someone to stay with them whereas someone else may say 'thanks for letting me know' and close the door."