The remains of two bodies have been passed to Britain by the Iraqi authorities, Foreign Secretary David Miliband has said.

There is no immediate confirmation of who they were, Mr Miliband said, but the Government's thoughts are with the families of five British hostages who were taken captive in Baghdad in May 2007.

"This is terrible moment of uncertainty and fear for them," he said.

Mr Miliband described the developments as "distressing".

"We do not yet have confirmation of who they are. Forensic examinations are under way to establish their identities and the causes of death as soon as possible.

"Our immediate thoughts are clearly with the families of the five Britons taken hostage in Baghdad in May 2007."

Mr Miliband added: "As would be the case with any development of this kind, they will fear the worst for their loved ones."

He said the Foreign Office is in close touch with the hostages' families and urged the media to "give them as much space as possible in these very difficult hours and days".

"Hostage-taking is never justified in any cause. Today's terrible news underlines the gravity of the crimes associated with it."

He reiterated Britain's call for the immediate safe release of "all the remaining hostages".

"I also confirm that we are working intensively towards that goal but I also have to say the threat to them remains very high indeed."

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