Islamic State of Iraq and the Levant (ISIS), an offshoot of al Qaeda, has taken over Tikrit, the hometown of former leader Saddam Hussein, the BBC reported. The offensive is considered a major move by the rebels, who have been escalating their insurgency this past week, and it has put the Shi'ite-led government on the defensive. Tikrit is 95 miles north of Iraq's capital, Baghdad.

As the Sunni insurgents gained control of Tikrit, they closed in on the largest oil refinery in Iraq.

The militants’ first major threat came when they seized the northern city of Mosul earlier in the week, Reuters reported.

Iraqi PM Nouri Maliki vowed to fight against the jihadists and punish anyone who didn’t resist or who fled, the BBC said. About 500,000 Iraqis have exited Mosul to seek sanctuary in the autonomous Kurdistan region.

"Our forces were caught by surprise, they never expected ISIL would use police and army Humvee vehicles, we mistook them for government forces and it was too late to stop them," a police captain said, according to Reuters. "We are fighting devils and not ordinary people."

Witnesses said they heard heavy gunfire in different parts of Tikrit on Wednesday afternoon. "The police didn't fight at all and withdrew one-by-one," a source told USA Today.

Militants freed prisoners in Tikrit and captured government buildings, according to the newspaper. And thousands have also begun to flee Tikrit. "I left the city with my family to stay in a village after I saw everything crumbling," Mahmoud Al Samaraie, 38, told USA Today. "I don't know for how long I will stay there. There is no electricity and no clean water. I fled just to protect my children. They were very scared because of all of this."

The Pentagon said "the situation remains fluid and the situation on the ground remains murky." There are rumors that U.S. military equipment has been commandeered by the militants, but the Pentagon would not comment on that directly.  

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