The pair are among 27 oil workers kidnapped by militants in September
Two Britons who have been held hostage in Nigeria for four months are "alive and well", according to their captors.
The Movement for the Emancipation of the Niger Delta (Mend) have released the first photographs of Robin Barry Hughes and Matthew John Maguire.
The pair were among 27 oil workers kidnapped by militants when their vessel was hijacked on 9 September.
Mr Maguire, from Birkenhead, Merseyside, and Mr Hughes appear to be well and uninjured in the pictures.
Mr Maguire was taken from a boat on his way to work on an oil rig and the photographs were the first his family have seen since the 34-year-old diver was abducted in September.
Mend said the two Britons would not be released until the Nigerian government frees the group's leader, Henry Okah, who is currently being tried on charges of arms trafficking.
In an e-mail sent to journalists, the group said: "Since their fate is now tied to his, God forbid that Henry Okah should die in detention."
It added they were "alive and well" and that the militants would continue to kidnap "high value oil workers from Western Europe and North America" in 2009 to keep pressure on the government to empower the inhabitants of Nigeria's oil-rich states.
The Foreign Office has called for their "immediate and unconditional release".
A spokeswoman said: "We remain in close contact with their families and our thoughts are with them at this deeply distressing time."