Tens of thousands of Sunni Muslims blocked Iraq's main trade route to neighboring Syria and Jordan in a fourth day of demonstrations on Wednesday against Shi'ite Prime Minister Nuri al-Maliki.
The massive show of force marks an escalation in protests that erupted last week after troops detained the bodyguards of Sunni Finance Minister Rafaie Esawi, threatening to plunge Iraq deeper into political turmoil.
"The people want to bring down the regime," chanted thousands of protesters in the Sunni stronghold of Anbar, echoing the slogan used in popular revolts that ended in the toppling of the leaders of Tunisia, Egypt, Libya and Yemen.
Waving the old flag of Iraq that was changed after Sunni dictator Saddam Hussein was overthrown by the U.S.-led invasion of 2003, protesters sat in the road, choking off the main trade route between Iraq, Jordan and Syria.
Another smaller protest was held in the city of Samarra in the predominantly Sunni province of Salahuddin, next to Anbar.
The move against Esawi's guards came hours after President Jalal Talabani, a Kurd who has mediated among Sunni, Shi'ite and Kurdish factions, left for Germany for treatment for a stroke that could end his steadying influence over Iraqi politics.
The arrest was reminiscent of Maliki's move to arrest Sunni Vice President Tareq al-Hashemi, who he accused of running death squads, just as U.S. troops withdrew in December 2011.
Iraq's fragile power-sharing government has since lurched from crisis to crisis and the conflict in Syria risks reigniting sectarian tensions that brought the country to the brink of all-out civil war in 2005-2007.
Addressing the protesters, Esawi said the detention of his guards was politically motivated and that Maliki was deliberately provoking strife.
"It is enough! The country should not be run by such a mentality," he said, to cries of "God is greatest".
Maliki has sought to play his rivals off against one another to strengthen his alliances in Iraq's complex political landscape before provincial elections next year and a parliamentary vote in 2014.
Shi'ite cleric Moqtada al-Sadr, another rival of Maliki, offered his support to the protests in a statement, rejecting what he described as Maliki's sectarian policies.