In a tape posted on the Internet Wednesday, al-Zarqawi said, "You have let us down in the darkest circumstances and handed us over to the enemy. ... You have quit supporting the mujahedeen."
The authenticity of the tape could not be confirmed. "Hundreds of thousands of the nation's sons are being slaughtered at the hands of the infidels because of your silence."
Al-Zarqawi, who leads the al-Qaida terror group in Iraq, is believed to have escaped from his headquarters in the Iraqi city of Fallujah during the U.S.-Iraqi assault earlier this month meant to root out insurgents.
"You made peace with the tyranny and handed over the countries and the people to the Jews and Crusaders ... when you resort to silence on their crimes ... and when you prevented youth from heading to the battlefields in order to defend the religion," he said, reported the Associated Press.
"Instead of implementing God's orders, you chose your safety and preferred your money and sons. You left the mujahedeen facing the strongest power in the world. Are not your hearts shaken by the scenes of your brothers being surrounded and hurt by your enemy?" he asked.
It was unclear when the tape was made or if al-Zarqawi was threatening the Sunni religious establishment, which has come under attack recently with the slaying of two Sunni clerics by gunmen this week.
Both clerics -- one slain in the northern city of Mosul and the other in the town of Muqdadiyah north of Baghdad -- were members of a Sunni group that had called for a boycott of Jan. 30 national elections because of the U.S.-led offensive against Fallujah, according to the AP.
There was no claim of responsibility for the two deaths.
Al-Zarqawi's group is believed to be responsible for dozens of deadly bombings and beheadings of foreigners.
The United States has placed a bounty of $25 million on al-Zarqawi's head.
Meanwhile, in Mosul, five more bodies were found, bringing the total to 20 discovered in the city in the past week.
It was not yet clear if the bodies were those of Iraqi security forces, said Lt. Col. Paul Hastings with Task Force Olympia. Previously, U.S. troops found 10 bodies of Iraqi soldiers, nine of them shot execution-style. Five other bodies, four of them decapitated, have not yet been identified.