Islamic groups including one led by Al Qaeda ally Abu Musab al-Zarqawi have vowed to take their battle in the rebel city of Fallujah to all corners of Iraq.
In a video obtained by the media, a masked gunman reading a joint statement from several militant groups also warns Iraqi government workers and soldiers will be targeted unless they stop work immediately.
The video, obtained by Reuters in Fallujah, showed three masked men carrying assault rifles and a rocket-propelled grenade launcher.
The tape could not be immediately authenticated.
"In response to the crimes and mass annihilation the Muslims of Fallujah are facing, the groups Qaeda Organisation of Jihad in Iraq, the Islamic Army, the 1920 Revolution Brigades ... announce the spread of the battle to all governorates and parts of Iraq," one gunman read from a handwritten piece of paper.
"We warn all employees in the Government and ministries, both civilian and military, not to go to work and to announce civil disobedience because remaining at work is doing a service to the Americans and collaborator Government.
"Anyone who does otherwise will make himself a target for us."
Essential services such as health, water and electricity were exempt, he said.
Some of the 11 groups named have claimed some of the bloodiest bombings, killings and kidnappings in Iraq.
US-led forces began a major offensive against Fallujah last Monday, aimed at clearing it of foreign Islamic militants and Saddam Hussein loyalist guerrillas.
US and Iraqi officials have acknowledged many fighters, including Zarqawi himself, probably fled the city ahead of the assault that residents say has caused heavy civilian suffering.
Violence has spiked in several cities across Iraq since the start of the offensive, much of it in the form of attacks on police and National Guards, whom insurgents opposed to the US presence in Iraq view as collaborators.
"All citizens must stay away from places where American troops, pagan army and collaborator police are present," the gunman warned in the video.
