The Foreign Office is checking unconfirmed reports on an Arab TV station that British hostage Kenneth Bigley has been killed by Iraqi militants.
Kenneth Bigley's brother Paul is praying the reports are not true
Abu Dhabi Television said it was told by "informed" sources in Iraq.
Mr Bigley, 62, of Liverpool, was taken hostage on 16 September by the Tawhid and Jihad group which beheaded two Americans captured at the same time.
The Foreign Office has informed Mr Bigley's family of the reports but says it cannot confirm them.
The Abu Dhabi TV says it has received a video CD relating to Mr Bigley, according to BBC correspondent Jo Floto.
The station refused to say what was on it but said that they would air it at 1500 BST.
It is not the first time it has been reported that Mr Bigley has been killed.
A previous claim on a website was quickly dismissed as unreliable.
On Friday, Reuters news agency also quoted Falluja insurgent sources as saying Mr Bigley had been killed on Thursday.
And Dubai-based news channel Al-Arabiya TV said its sources confirmed the execution of Mr Bigley.
Commenting on the latest reports, Mr Bigley's brother Paul, who has led a campaign for the engineer's release told Reuters: "I have heard nothing at all.
"I have been optimistic and remain optimistic."
He said he was praying the news was not true.
A Foreign Office spokesman said it was "trying urgently to corroborate reports that Kenneth Bigley has been killed but has not yet done so".
The Foreign Office was "in close touch with the family at this difficult time", he added.
Iraqi Interior Ministry officials in Baghdad said they had no information on the report, Reuters said.
Mr Bigley was last seen alive in a video broadcast last week, pleading for Prime Minister Tony Blair to help him.
An Iraqi cleric claimed to have met Mr Bigley last Saturday.
Syed al-Kareem said part of the reason Mr Bigley had not been executed was because his captors were trying to determine if he is Irish or British.
Ireland has now granted a passport to Mr Bigley, whose mother was born in Dublin.
His Irish citizenship has formed part of a campaign for his freedom, led by his brother Paul.