The BBC said last night it was "deeply concerned" by reports that its kidnapped Gaza correspondent, Alan Johnston, had been killed.

Mr Johnston, originally from Scotland, was taken by masked gunmen as he returned to his apartment in Gaza City on March 12.

The BBC said in a statement: "We are deeply concerned about what we are hearing, but we stress at this stage it is rumour with no independent verification."

A Foreign and Commonwealth Office spokeswoman said: "We are aware of these reports and are urgently looking into them."

Mr Johnston, the only Western reporter permanently based in Gaza, had been preparing to leave because his three-year placement was due to finish at the end of last month.

A previously unknown Palestinian group, "The brigades of Tawheed and Jihad", claimed it had killed Mr Johnston in a statement sent to news organisations.

But the Palestinian government said there was no evidence to support the claim.

Although the group is not known in Gaza, the name has been used elsewhere in the Middle East by organisations linked to al Qaida.

Palestinian Interior Minister Hani Kawasmeh told a press conference in Gaza City: "This party that issued the statement about the so-called killing is unknown to the security services.

"There is no information to confirm the killing of Johnston until now."

The group claimed it killed Mr Johnston, 44, to support demands for the release of Palestinian prisoners held by Israel.

Thousands of people from around the world have signed a petition calling for Mr Johnston's release and hundreds have also posted messages of support on the BBC News website.