The protests have grown in recent weeks. They began in late December when Sunni demonstrators took to the streets in Anbar province, which borders Jordan and Syria, to protest al-Maliki's order to arrest the bodyguards of Finance Minister Rafaie al-Esawi, a Sunni.
The arrest of al-Esawi's bodyguards came just hours after President Jalal Talabani, a Kurd who is widely viewed as a stabilizing political force in Iraq, left the country about two weeks after suffering a stroke.
The protesters also are demanding the release of detainees they said are held without charges, calling the government corrupt and accusing it of unfairly targeting Iraq's Sunni people.
Iraq's Arab Sunnis and Kurds have accused al-Maliki and his Shiite political party of working to consolidate power in Iraq by cutting them out of the political process, an allegation that comes as U.S. lawmakers raise concerns about Iraq strengthening its ties with Shiite-dominated Iran.
Sunnis make up about 20% of Iraq's estimated population of more than 27 million, whereas about 60% to 65% are Shiite.
Since the fall of Saddam Hussein's Sunni-dominated regime in 2003, Sunnis in Iraq have been largely disaffected. The gulf was widened in 2005 when Sunnis boycotted the country's election, opening the way to a heavily dominated Shiite government.
The sectarian divisions translated into violence in the streets in 2006 and 2007, with fighting that nearly ripped the country apart.