BAGHDAD (AP) -- Islamic State militants launched an attack against government troops Sunday outside the militant-held city of Fallujah, killing at least 17 troops, officials said.
Four suicide attackers drove explosives-laden military vehicles into government forces' barricades outside Fallujah, west of Baghdad, the officials, a police officer and an army officer, said. Clashes broke out afterward. The officials said 15 other troops were wounded.
Both officers spoke on condition of anonymity as they were not authorized to release information.
The fall of Fallujah in January 2014 started the Islamic State group's dramatic blitz across Iraq. Since then, Islamic State group fighters have been advancing in Anbar province, the heartland of Iraq's Sunni minority. Iraqi troops 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 Sunday he will launch an investigation to probe commanders who withdrew from Ramadi without orders, leaving it to fall to the Islamic State group.
A statement from al-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," his office said in a statement.
The ministries of defense and interior will form investigative boards to look into why troops abandoned their weapons and equipment while fleeing, the statement added.
Backed by Shiite and Sunni paramilitary forces, Iraqi government forces last month launched a wide-scale military operation to dislodge militants from Fallujah and other key cities in Anbar province. Central Command spokesman Col. Pat Ryder said 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," he said, using an acronym for the militant group.