"The American invader forces claim that al-Zarqawi, and with him a group of Arab fighters, are in our city," a masked man read from a piece of paper on Friday.
"We know that this talk about al-Zarqawi and the fighters is a game the American invader forces are playing to strike Islam and Muslims in the city of mosques, steadfast Falluja."
The United States believes al-Zarqawi, accused of leading a bloody campaign of bombings and of decapitating an American and a South Korean captive, has played a significant role in the violence gripping Iraq.
On the tape, five men holding a rocket-propelled grenade launcher and machine gun said local fighters were defending their hometown - sometimes known as the "city of mosques".
US occupation forces over the past week bombed houses they said were hideouts for al-Zarqawi's fighters.
A group led by al-Zarqawi, who Washington says has links to al-Qaida, claimed responsibility for a wave of attacks in Iraq on Thursday in which at least 100 people were killed and hundreds more wounded.
"We know that this talk about al-Zarqawi and the fighters is a game the American invader forces are playing to strike Islam and Muslims in the city of mosques, steadfast Falluja"
Masked man in video message
In one of the attacks, scores of black-clad fighters, some wearing headbands with the name of al-Zarqawi's group, attacked a police station and other government buildings in Baquba, northwest of Baghdad.
Iraq's interim national security minister said on Thursday that Iraqi officials had good intelligence on al-Zarqawi - who this week threatened to assassinate Iraq's prime minister - and plan to pursue him after the formal transfer of power next week.
The US has offered a $10 million reward for his capture.
In April, hundreds of Iraqis were killed in Falluja in fierce fighting between marines and fighters.
A truce was agreed to under which marines withdrew from the city and an Iraqi force took over responsibility for security.