A multi-faith service has been held to call for the safe return of BBC Gaza correspondent Alan Johnston.
Alan Johnston has been held captive for almost six weeks
People from different religious communities gathered for the vigil at St Martin in the Fields, London.
BBC deputy director general Mark Byford told the congregation that Mr Johnston was a "remarkable and courageous" journalist who was "driven by truth".
The 44-year-old reporter has not been seen since he was seized at gunpoint on his way home in Gaza City on 12 March.
Mr Byford said: "For the last 75 years the BBC has relied on an extraordinary group of people who go into the world's trouble spots, often just as everyone else is getting out.
"No-one is braver or has faced more hardship than Alan Johnston," he added.
London Mayor Ken Livingstone later made a public appeal for information on Arab TV, calling the journalist's abduction "a catastrophe".
Leading the London service, which was followed by a silence, the Reverend Nicholas Holtam said: "We unite in our shared belief under God that the kidnap of Alan Johnston is wrong."
Imam Dr Abdul-Jalil Sajid said: "We need to show our solidarity together, as a multi-faith... to hope that the kidnappers - maybe Christian, maybe Muslim, maybe anybody else - listen to us and release Alan very soon."
Rabbi Mark Winer, of the West London synagogue, said the kidnap of any journalist was a matter that transcended politics.
"People of every religion, race and background in the United Kingdom are concerned about his welfare and insist that regardless of their political motives, that the kidnapping of journalists is something that is utterly unacceptable in any part of our world."
BBC world news editor Jon Williams said he hoped the service would send an important message to Mr Johnston's captors that the abduction was "abhorred" by "those who follow Christian tradition... by Muslims across the world and people of the Jewish faith, and indeed people of no faith".
Journalists held a vigil in Pakistan to call for Alan Johnston's release
Mr Livingstone, during a live broadcast on Arab station Al Hiwar TV, said: "All the Palestinians needed was the truth to be reported, which is what Mr Johnston did.
"His abduction was a catastrophe. If you wanted to find a person whose abduction could damage the Palestinian cause, you couldn't find anyone better to do the job."
Appealing directly to Johnston's kidnappers, the mayor said: "Look what you have done.
"Instead of the foreign media continuing to report on the situation in Palestine, the media focus has been shifted to the story of the kidnapping."
One of the presenters was Anas Altikriti, of the Muslim Association of Britain, who went to Iraq to negotiate for the release of British hostage Norman Kember in 2006.
Mr Altikriti said Mr Johnston's abductors "don't serve the best interests of the Palestinians or the people of Gaza".
Meanwhile, local journalists and foreign correspondents in Islamabad, Pakistan, have held a vigil for Mr Johnston.
Among them were several former colleagues who worked with him when he served as the BBC's Kabul reporter in 1997 and 1998.
Palestinian President Mahmoud Abbas has insisted Mr Johnston is alive.
And Hamas political leader Khaled Meshaal has appealed for the immediate release of Mr Johnston.
Speaking in Damascus, Mr Meshaal said the kidnappers were harming the national interest of the Palestinian people.
An unknown militant group said a week ago that it had killed the correspondent, who has been working in the Gaza Strip for the past three years, but the BBC and Palestinian officials have said they have been unable to verify the claim.