Iraqi troops reportedly seized control of a strategic area in Baiji on Friday, clearing a route into the city's oil refinery, where fighting with Islamic State (IS) militants has raged for the last two months.

US Marine Brig. Gen. Thomas D. Weidley said in a statement Friday that Iraqi forces had made "steady, measured progress in regaining some of the areas leading to the Baiji oil refinery."

Weidley, chief of staff for Combined Joint Task Force Operation Inherent Resolve, the international campaign against IS, said the militants retaliated against the Iraqi advance with "IEDs [improvised explosive devices], suicide vehicle borne IEDs, as well as heavy weapon and rocket fire attacks."

Iraq's Interior Ministry said government forces were able to "severely" attack IS members at the oil refinery, and that they had cleared the main road from the city to the refinery, according to Rudaw, a Kurdish news agency.

A video released Sunday by Aamaq News Agency, an activist group that supports IS, shows parts of the refinery completely engulfed in flames with huge plumes of black smoke billowing into the night sky. Daylight footage in the same video shows fires smoldering among tangled piles of rubble.

The largest oil refinery in the country, Baiji has been at the center of battles between Iraq and IS forces for more than a year. The facility, located about 150 miles north of Baghdad, was initially captured by IS fighters last summer, but the Iraqis retook partial control in November with support from coalition airstrikes. Despite the gains, however, the Iraqis have been unable to completely push the IS forces out of the 14 square mile compound.

Earlier this month, an Iraqi federal police officer in the facility told the Iraq Oil Report, a site that tracks the country's oil and energy industries, that he and his troops were surrounded by IS members and running out of ammunition and supplies.

"All of us now are thinking of committing suicide," the police officer reportedly said. "We have very little food and ammunition, and we can't withstand the suicide bombers, snipers, and rockets."

The battle for the oil field has taken on added significance following the recent militant capture of Ramadi, the capital of Anbar, Iraq's largest province. US Secretary of Defense Ashton Carter said on Sunday that Iraqi troops were not outnumbered in Ramadi, and had left behind key military weapons and supplies as they fled the city.

"What apparently happened is the Iraqi forces just showed no will to fight," Carter said on CNN. Using an alternate acronym for the Islamic State, the Pentagon chief added, "They were not outnumbered; in fact, they vastly outnumbered the opposing force. That says to me, and I think to most of us, that we have an issue with the will of the Iraqis to fight ISIL and defend themselves."

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