Johnston's parents "desperately" worried

The parents of missing journalist Alan Johnston have issued a statement in response to last night's claim by a previously unknown group that their son has been killed.

"This is a desperately worrying time for us," said Graham and Margaret Johnston. "We make a heartfelt appeal to anyone who may have knowledge of Alan's situation and well-being to contact the authorities in Gaza. Our son has lived and worked among the people of Gaza for the last three years to bring their story to the outside world and we ask every one of them to help end this ordeal."

Late last night, a group calling itself the Al Tawhid Al Jihad brigades ("Brigades of Holy War and Unity") faxed numerous news organisations with a claim that it had killed Johnston. The BBC, Foreign Office and Palestinian authorities have each said they are investigating the claim but that at the moment it is an unsubstantiated rumour.

"The BBC has still had no independent verification of rumours concerning Alan Johnston," the BBC said this morning. "We continue to be highly concerned for his safety and are working closely with the Palestinian and British authorities to seek urgent clarification. Our thoughts are with Alan's family, and we appeal to those who have taken him to release him unharmed."

Johnston is understood to have been kidnapped in Gaza on March 12.