Security forces defend their headquarters against attacks by ISIS extremists during sand storm in the eastern part of Ramadi.

Iraqi forces broke a siege on the country’s largest oil refinery by Islamic State of Iraq and Syria (ISIS) militants on Thursday, liberating around 300 soldiers who were held hostage in the area, sources told Al Arabiya News Channel.

In early May, U.S. forces were trying to relieve pressure on Iraqi forces at the geographically important Baiji oil refinery, hitting militants with air strikes after ISIS seized the area.

The militants overran Iraqi government defenses east of the city of Ramadi on Thursday, police and pro-government tribal fighters said.

The defensive line was breached at Husaiba, about 10 kilometers from the city, on Thursday afternoon after ISIS fighters intensified mortar and rocket fire.

“The situation is very critical now after Daesh (ISIS) fighters managed to overrun our defensive line in Husaiba,” Police major Khalid al-Fahdawi said.

“We have retreated to the eastern part of the area and we’re waiting for more reinforcements and air force strikes to stop the Daesh advance.” Earlier, Iraqi forces said they thwarted a third attempt by ISIS militants to break through their defensive lines east of the city of Ramadi overnight on Thursday.

Police and pro-government Sunni fighters exchanged mortar and sniper fire with the insurgents across the new frontline in Husaiba al-Sharqiya, about halfway between Ramadi and a base where a counter-offensive to retake the city is being prepared.

Ramadi fell to the militants on Sunday in the most significant setback for Iraqi security forces in nearly a year, calling into question the U.S.-led strategy to “degrade and destroy” the Islamist group.

The militants are now seeking to consolidate their gains in the surrounding province of Anbar by pushing east towards the Habbaniya base where Iraqi security forces and Shi’ite paramilitaries are massing.

“Daesh is desperately trying to breach our defenses but this is impossible now,” Police major Khalid al-Fahdawi said, referring to ISIS. “We have absorbed the shock and more reinforcements have reached the frontline. They tried overnight to breach our defenses but they failed. Army helicopters were waiting for them.”

Habbaniya is one of only a few remaining pockets of government-held territory in Anbar, and lies between Ramadi and the town of Falluja, which has been controlled by ISIS for more than a year.

Local officials say the militants want to join up the two towns and overrun the other remaining government holdouts, strung out along the Euphrates river valley and the border with Jordan and Saudi Arabia.

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