After breaking a months-long jihadist siege of the Shiite Turkmen town of Amerli by Islamic State (IS) fighters, troops on Tuesday regained control of part of a key highway linking Baghdad to the north.
Two towns north of Amerli were also taken from the jihadists on Monday as Iraqi forces -- backed by US air strikes -- score their first major victories since the army's collapse across much of the north in June.
That collapse left some 1,700 soldiers in jihadist hands, with many believed to have been executed.
Demanding to know their fates, angry relatives stormed parliament in Baghdad, attacked MPs and began a sit-in in its main chamber, an official said.
Anti-riot police were trying to evict the hundreds of protesters, who were also calling for some officers to be held accountable, said the official, who was present at parliament.
Concern over those in jihadist hands has been fuelled by reports of widespread atrocities, including accusations from Amnesty International of war crimes and ethnic cleansing.
The Sunni extremist IS declared an Islamic "caliphate" in regions under its control in Iraq and Syria after it swept through much of the Sunni Arab heartland north of Baghdad in June and then stormed minority Christian and Yazidi Kurdish areas.
IS has carried out beheadings, crucifixions and public stonings, and Amnesty on Tuesday accused it of "war crimes, including mass summary killings and abductions" in areas it controls.
'Wave of ethnic cleansing'
"The massacres and abductions being carried out by the Islamic State provide harrowing new evidence that a wave of ethnic cleansing against minorities is sweeping across northern Iraq," said its senior crisis response adviser Donatella Rovera.
The UN Human Rights Council unanimously agreed to send an emergency mission to Iraq to investigate IS atrocities, after a senior UN official said the jihadist group had carried out "acts of inhumanity on an unimaginable scale".
Concern over the scale of the humanitarian crisis helped prompt limited US air strikes in support of Iraqi forces, Shiite militia and Kurdish troops battling the jihadists.
Such strikes were used in the area during the Amerli operation -- the first time Washington has expanded its more than three-week air campaign against IS outside the north.
Desperate residents rushed to receive aid deliveries after Iraqi forces moved in to the town, scrambling to grab food and bottles of water from flatbed trucks.
A day after seizing Amerli, troops and Shiite militiamen on Monday retook Sulaiman Bek and Yankaja, two towns to its north that had been important militant strongholds.
Army staff lieutenant general Abdulamir al-Zaidi said they had continued the advance on Tuesday, regaining control of a stretch of the main highway to the north which had been closed by the militants for almost three months.
A senior militia commander said it would be several days before the road reopened as sappers needed to clear it of mines and booby-traps planted by the retreating militants.
The United States said it launched four air strikes in the Amerli area, meaning that it effectively supported operations involving militia forces that previously fought against US troops in Iraq.
The government's reliance on Shiite militiamen in this and other operations risks entrenching groups which themselves have a history of brutal sectarian killings.
David Petraeus, a former commander-in-chief of US-led forces in Iraq, has warned against America becoming an "air force for Shiite militias".
But worries over the rise of IS seem to be outweighing other concerns, with Western leaders warning the group poses a security risk far outside the areas under its control.
Demands for UN hostages
Australian Prime Minister Tony Abbott on Tuesday said that "extreme force" was justified against IS militants, describing them as worse than Nazis or Communists.
"As soon as they've done something gruesome and ghastly and unspeakable, they're advertising it on the Internet for all to see which makes them, in my mind, nothing but a death cult," Abbott said.
Fiji, meanwhile, revealed that Al-Qaeda-linked Syria rebels who are holding 45 United Nations peacekeepers hostage in the Golan Heights are demanding they be expunged from a UN terror blacklist.
The Fijians, part of the UN Disengagement Observer Force (UNDOF), were captured last Wednesday when Al-Nusra Front rebels stormed a Golan Heights crossing.
Another group of 75 Philippine peacekeepers refused to surrender and eventually escaped from two camps on the Syrian side of the demarcation line after the rebels besieged them.
Fiji's army chief Mosese Tikoitoga said a UN team had arrived in the Golans from New York to take over negotiations for their release.
"Unfortunately we have not made any improvement in the situation, our troops remain at an undisclosed location, the rebels are not telling us where they are," Tikoitoga said, adding that the hostage-takers also want humanitarian aid for areas they control and compensation for wounded fighters.