Sunni leaders in Anbar have threatened to launch attacks against the army in the western Iraqi province after five protesters were shot dead in Fallujah.
The anti-government demonstrators were killed and 60 others injured in clashes with soldiers after Friday prayers.
Tribal leaders say they have given the government one week to arrest those soldiers responsible for opening fire on the crowd.
They say they will then attack army units and posts across the province.
Friday's protest was the first such confrontation with the army since mass protests against the Shia-led government began five weeks ago in Baghdad and western Iraq.
The protesters accuse the government of discrimination against Sunni Arabs, saying they are treated as second-class citizens, and demand the resignation of Prime Minister Nouri Maliki, a Shia Arab.
Sheikh Ahmed Abu Risha, who chairs the Sahwa or Awakening Council in Anbar - a group which has proved vital in fighting al-Qaeda in Iraq in recent years - said the tribal leaders had given the central government a week to bring the soldiers responsible for Friday's deaths "to justice" before Sunni fighters started "targeting the army".
"If the government has not heeded our demand, we will launch jihad against army units and posts in Anbar," warned Mr Risha, who was reading a statement from a podium in Fallujah's main square - the sight of a sit-in protest.
"There is no excuse whatsoever to shoot at demonstrators. And we will target army posts in all cities and towns across the province if the government ignores our demand," he told the BBC.
Sheikh Abu Risha said the soldiers must stand trial in Anbar, because the judiciary in the capital, Baghdad, was over-politicised.
The demonstration in Fallujah was one of several held in the mainly Sunni province on Friday.
Friday's violence in Fallujah broke out after after army units in the west of the city stropped protesters from joining up with the main demonstration in the city centre.
The protesters retaliated by throwing bottles of water and stones at the troops, who then opened fire.
It was not immediately clear whether the soldiers had fired directly into the crowd or into the air.
The army said the protesters were trying to cut off an international road linking Iraq with neighbouring Jordan and Syria.
Hours after Friday's shootings, police told the BBC that gunmen had attacked an army checkpoint in the district of al-Setcher, in northern Fallujah.
The Associated Press cited a police official as saying two soldiers were killed.
The anti-government protests began in mid-December shortly after the arrest of several bodyguards of Finance Minister Rafie al-Issawi, the most high-profile Sunni Arab in the cabinet.
But the campaign against Mr Maliki has since broadened.
Sunnis believe they are disadvantaged when trying to find work, that the laws are unequally applied and that the government is in the sway of Shia Iran.
Demonstrators say anti-terrorism laws are being used as an excuse to detain members of the Sunni community.
Mr Maliki has urged both the security forces and demonstrators to show restraint, warning that Iraq may be pushed towards sectarian conflict.
"The government has already started implementing some of the [protesters'] demands, like the release of hundreds of prisoners," government spokesman Ali al-Mousawi told the BBC.
"The prime minister suggested dissolving parliament and holding early elections to defuse the crisis. But unfortunately there are some protesters who have hidden political and sectarian agendas."