The video — as grisly as any the al Qaeda in Iraq leader issued — was clearly designed to quash hopes that the Sunni-dominated insurgency might change tactics by ending attacks on Shiite civilians and institutions, especially the police.
Fellow Sunni insurgent groups sent condolences for al-Zarqawi in Internet messages Saturday and warned Sunnis not to cooperate with the Iraqi government, an apparent call for unity three days after U.S. forces killed the terror leader in a targeted airstrike.
The condolence statements came from the al Qaeda-linked Ansar al-Sunnah — the group that posted the beheading video on a militant Web site — and the head of the Mujahedeen Shura Council, an umbrella organization of five insurgent groups, including al Qaeda in Iraq, that al-Zarqawi helped found last year.
"Iraq is the front defense line for Islam and Muslims, so don't fail to follow the path of the mujahedeen (holy warriors), the caravan of martyrs and the faithful," said Abdullah bin Rashid al-Baghdadi, the Shura Council's head.
He vowed: "As for you the slaves of the cross (coalition forces), the grandsons of Ibn al-Alqami (Shiites), and every infidel of the Sunnis, we can't wait to sever your necks with our swords."
Across Iraq, at least 24 people were killed in violence Saturday — including a number of sectarian attacks.
Gunmen stopped a minivan carrying Sunnis on a highway near Baghdad, ordered the passengers off and opened fire, killing four and wounding one. In Baghdad, gunmen in two cars shot dead a Shiite metal worker and wounded two others. Also in the capital, a roadside bomb exploded in the mainly Shiite Karadah area, targeting a police patrol; five people were killed and 14 wounded, including three officers.
In the northern city of Mosul, gunmen killed three Shiite butchers.
The Jordanian-born al-Zarqawi was the defining face of Iraq's insurgency. His tirades against the nation's majority Shiites and calls on the once-dominant minority Sunni Arabs to rise up and kill them were matched by the killing of thousands of Shiites in attacks.
In contrast, Ansar al-Sunnah has largely refrained from killing civilians. Made up mostly of homegrown Iraqi guerrillas, the group instead has mostly gone after American and Iraqi forces as well as Iraqis and foreigners employed by the U.S. military.
In other developments:
It was the first known footage of beheadings to be posted by any insurgent group in months, and possibly timed to make clear to the U.S. and Iraqi governments that there will be no change in tactics even though al-Zarqawi is gone.
With its gruesome killings and militants chanting "Allahu Akbar", or "God is Great," the 15-minute video illustrates the depth of Shiite-Sunni rivalries.
It shows three men in military uniform, sitting on the ground with their hands bound behind their backs in a small concrete room with gunmen standing around them.
Under questioning, the men say they are members of the "Wolf Brigade," a special Iraqi police commando unit that Sunnis accuse of being a front for Shiite militiamen who kill Sunni Arabs.
Text in the video says the three were part of a "Shiite death squad" that kidnapped and killed Sunnis at checkpoints south of Baghdad in March and April. It says they were among 10 police commandos captured by Ansar al-Sunnah last month.
A militant off-camera asks them about the incident and other alleged slayings of Sunnis. The men reply in low voices, looking terrified. One mostly stares with his mouth hanging open.
"They (the Sunnis) were beheaded by those who took and detained them," one of the three says. Next the video shows the three captives lying on the ground outdoors. A militant sharpens a knife before he, with the help of others, beheads the men one by one.
At the end of the tape, the group warns Iraqis against joining the security forces: "Otherwise, you will live in terror until we eliminate you and your fate will be in hell."
Iraqi and U.S. leaders have acknowledged that al-Zarqawi's killing was not likely to stop the insurgency, now in its fourth year. But they hoped it would rob his supporters of an iconic figure around which they rallied.
The U.S. military has moved quickly to take advantage of the , carrying out at least 56 raids since Wednesday's airstrike pulverized his hideout in a remote village northwest of Baghdad.
A search of the destroyed safe house yielded documents and electronic storage devices, all being assessed for potential use against his followers, a U.S. military officer has said.
Investigators also found documents and unspecified "media," which the officer indicated usually means information storage devices such as computer hard drives and digital cameras. The officer spoke on condition of anonymity because the search results have not been formally announced.
At the scene of the airstrike, a floral-pattern pillow, a torn mattress, sandals, and a red blanket lay scattered among the debris of concrete blocks and twisted steel, according to Associated Press Television News footage.
An air conditioner and part of a washing machine also could be seen in the area, where ripening pomegranates hung from a remaining tree. Pieces of women's clothing also were found in the rubble.
Beside al-Zarqawi, the airstrike also killed his spiritual adviser, two men, two women and a girl estimated between the ages of 5 and 7.