Iraqi government forces have reached within a kilometre of the country’s biggest oil refinery, two army officers and a witness have said.

It is the closest they have come to breaking an Islamic State in Iraq and the Levant (ISIL) siege of the facility during months of fighting, Reuters news agency reported.

Fighting raged in a village between the complex and the nearby town of Baiji, near a deserted area believed to contain roadside bombs planted by ISIL fighters that has been preventing an advance, the army officers said.

“Daesh (ISIL) militants are escaping to the direction of a river. Airplanes are targeting them,” said an army captain.

A witness said security forces had crossed a bridge close to the refinery, 200km north of the capital.

ISIL fighters seized the city of Baiji and surrounded the sprawling refinery in June during a lightning campaign through northern Iraq.

The group also controls territory in neighbouring Syria and has proclaimed a caliphate straddling both countries.

Iraq’s army initially put up little resistance to Islamic State. But it has been helped in recent weeks by US-led air strikes on ISIL positions.

Iraqi Prime Minister Haider al-Abadi sacked 26 military commanders this week for corruption and incompetence in the aftermath of ISIL advance.

In September, he retired two senior generals as part of an overhaul of the country’s armed forces.

Speaking through an aide after Friday prayers, Iraq’s top Shia cleric, Grand Ayatollah Ali-al Sistani, reiterated his criticism of corruption in the military.

He also called on the government to get its finances in order, fund projects and create jobs. Al Jazeera