The Islamic State of Iraq and the Levant (ISIL) has carried out an attack against Iraqi forces outside the city of Fallujah, west of Baghdad, killing at least 15 soldiers, officers have said.
Four suicide attackers drove explosives-laden military vehicles into government forces' barricades outside Fallujah, a police officer and an army officer told the AP news agency.
The officials said 15 other troops were wounded.
Both officers spoke on condition of anonymity as they were not authorised to release information.
In a seperate attack in Baiji in Salahuddine province, ISIL launched an attack on Iraqi forces killing several troops, the commander of operations in Salahuddine province said.
Rukn al-Jumaa also said that due to the deadly clashes, Iraqi forces had had to retreat in some areas of Baiji.
Fall of Fallujah
The fall of Fallujah, in January 2014, saw the start of an ISIL advance across large areas of Iraq, including Anbar province, the heartland of Iraq's Sunni minority.
Iraqi forces lost the provincial capital, Ramadi, in May after more than a year of fierce clashes. Tens of thousands of civilians have fled the province amid continued fighting.
Iraq's prime minister Haider al-Abadi said on Sunday he would launch an investigation into the commanders who withdrew from Ramadi without orders, leaving it to fall to ISIL.
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A statement from Abadi's office said the prime minister approved "decisions to refer a number of leaders to military tribunal for leaving their positions without a warrant and contrary to instructions, despite several orders not to withdraw".
The ministries of defence and interior will form investigative boards to look into why troops abandoned their weapons and equipment while fleeing, the statement added.
The parliamentary investigation also held former premier Nuri al-Maliki and 35 others responsible for the fall of Mosul last year, politicians said on Sunday.
The report detailing the findings of the investigation has been presented to parliament speaker Salim al-Juburi, who said it will be sent to the prosecutor general for legal action.
Backed by Shia and Sunni paramilitary forces, Iraqi government forces last month launched a wide-scale military operation to dislodge fighters from Fallujah and other key cities in Anbar province.
Central Command spokesman Colonel Pat Ryder said on Friday that Iraqi security forces are "encircling" Ramadi, in order to "tighten the noose around ISIL's neck in this city before commencing ... the seize aspect of the operation".
Source: Al Jazeera and agencies