Condemning the 30 January elections to elect a national assembly that will draft a new constitution, he said: "In the balance of Islam, this constitution is infidel and therefore everyone who participates in this election will be considered an infidel."
"Beware of henchmen who speak in the name of Islamic parties and groups who urge people to participate" in the election.
Describing al-Zarqawi as the "amir" of al-Qaida in Iraq, he called upon Muslims there "to listen to him".
Endorsing al-Zarqawi was "a great step on the path of unifying all the mujahideen in establishing the state of righteousness and ending the state of injustice".
Al-Zarqawi and his men are fighting "for Allah's sake. We have been pleased that they responded to God's and his Prophet's order for unity, and we in al-Qaida welcome their unity with us", he said.
Believed to be hiding in the mountains along the Pakistan-Afghanistan border, the Saudi-born bin Laden last sent a video message to Aljazeera before the US presidential elections.
