CAIRO, Egypt — Iraqi insurgent groups closed ranks in response to the death of al-Qaida leader Abu Musab al-Zarqawi, sending condolences in Web messages Saturday and warning Sunnis not to cooperate with the Iraqi government.

One group, Ansar al-Sunna, posted a video showing militants interrogating and then beheading three Iraqis accused of belonging to a Shiite "death squad" that killed Sunnis.

An early signature of the insurgency, videos of beheadings have become rare in the past year. The posting of one now on a militant Web forum suggests an attempt to show that al-Zarqawi's death has not weakened their resolve.

The condolence statements came from Ansar al-Sunna and the head of the Mujahedeen Shura Council, an umbrella organization of five insurgent groups — including al-Qaida in Iraq — that al-Zarqawi helped found last year.

Abdullah bin Rashid al-Baghdadi, the Shura Council's head, vowed to continue the fight.

"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," al-Baghdadi said, addressing militants.

"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."

Ansar al-Sunna vowed to break attempts at political progress in Iraq.

"To all Muslim everywhere, the battle is still going on and has reached its peak. Our next phase is to make the new plans (of the U.S. and Iraqi governments) fail, like the previous ones," said the statement, signed by the group's "emir," or leader, Abu Abdullah al-Hassan bin Mahmoud.

"To the slaves of the cross, and their agents, listen to our loud anger, which will deafen you and paralyze your forces," he said.

Followers of the Jordanian-born al-Zarqawi were notorious as the most ruthless insurgents in Iraq, conducting suicide bombings against Shiite civilians and kidnapping and beheading Western hostages.

But Ansar al-Sunna — believed to be made up mainly of homegrown Iraqi guerrillas — has never been far behind.