More than 20 people have been killed in clashes between security forces and Sunni Arab protesters in northern Iraq, officials say.
Violence erupted when security forces raided an anti-government protest camp in Hawija, near Kirkuk.
Two Sunni ministers said they were resigning in protest over Tuesday's raid.
It was the worst violence between security forces and Sunni protesters in recent months.
Tens of thousands of Iraqis in Sunni-dominated areas have been protesting against Prime Minister Nouri al-Maliki, accusing his government of discriminating against them.
The government denies the accusations and says that protesters have been infiltrated by militant groups.
Hawija has been under siege since Friday when an Iraqi officer was killed in clashes with protesters. Residents refused a demand to hand the suspects over.
A final attempt at mediation broke down on Monday night and troops were sent in at dawn, the BBC Arabic's Rafid Jaboori reports from Baghdad. The government claimed its forces came under attack and had to respond.
The defence ministry said 20 "gunmen" and three officers were killed, while other officials said that as many as 27 people had died.
After the raid, Sunnis briefly seized control of three checkpoints near Hawija before the army, reportedly using helicopter gunships, retook them. A number of further deaths were reported as the checkpoints were attacked.
In Hawija, the army cleared the square where the protest camp had been set up, burning tents, Reuters news agency reported.
Call for restraint
The government said it would form a fact-finding committee on the Hawija incident, to be chaired by Sunni Deputy Prime Minister Saleh al-Mutlag.
But hours later Education Minister Mohammed Tamim and Science and Technology Minister Abdul Karim al-Samarrai, both Sunnis, said they were resigning. Two Sunni ministers had already resigned since March.
Tuesday's violence came despite a call by UN special envoy Martin Kobler for calm in Hawija.
With its massive oil reserves, Kirkuk - home to a mixture of Arabs, Kurds and Turkmen - is one of the most bitterly contested of Iraq's disputed territories.
The Kurds want to incorporate it into their largely autonomous region, while Arabs and Turkmen oppose any change to its current status, ruled directly from Baghdad.
Iraq is currently awaiting the results of provincial polls held on 20 April - the first elections since the last US troops withdrew at the end of December 2011.
There was widespread violence before the polls. Dozens were killed in bombings targeting mainly Shia areas last week, and 14 candidates, most of them Sunnis, were murdered.
The government said on Tuesday it would hold delayed votes in two Sunni-dominated provinces, Anbar and Nineveh, on 4 July.