Any Iraqi who voted on January 30 would be an infidel, a voice purporting to be Osama bin Laden's said on a tape broadcast by the Arabic channel Al-Jazeera.

US intelligence officials said the latest tape purporting to be from the al-Qaeda leader was found likely to be genuine after a technical analysis.

The speaker on the tape also praised the Jordanian rebel leader Abu Musab al-Zarqawi as an "emir", or prince, of the al-Qaeda organisation in Iraq, saying he was leading the fight against "the Americans and [interim Prime Minister Iyad] Allawi's renegade government".

"The groups affiliated with him are good," the speaker said. "We were pleased with their daring operations."

In the two-minute-long message, the speaker hailed Zarqawi as a "true soldier of God".

"The constitution imposed by the American occupier [Paul] Bremer is blasphemous ... and anyone who takes part in this election consciously and willingly is an infidel," the speaker said.