(Associated Press) - The Islamic State group seized control of the city of Ramadi on Sunday, sending Iraqi forces racing out of the city in a major loss despite the support of U.S.-led airstrikes targeting the extremists.

Online video showed Humvees, trucks and other equipment purportedly speeding out of Ramadi, with some soldiers gripping onto their sides. Prime Minister Haider al-Abadi ordered security forces not to abandon their posts across Anbar province, apparently fearing the extremists could capture the entirety of the vast Sunni province that saw intense fighting after the 2003 U.S.-led invasion of the country to topple dictator Saddam Hussein.

The retreat recalled the collapse of Iraqi police and military forces last summer, when the Islamic State group's initial blitz into Iraq saw it capture about a third of the country. It also calls into questions American officials hopes of relying solely on airstrikes to support the Iraqi forces in expelling the extremists.

"Ramadi has fallen," said Muhannad Haimour, a spokesman for the governor of Anbar province. "The city was completely taken. ... It was a gradual deterioration. The military is fleeing."

Earlier Sunday, al-Abadi also ordered Shiite militias to prepare to go into the Sunni-dominated Anbar province, ignoring worries their presence could spark sectarian bloodshed apparently over fears the extremists could seize more territory.

The final push by the extremists began earlier Sunday, when police and army officials said four nearly simultaneous bombings targeted police officers defending the Malaab district in southern Ramadi, killing 10 and wounding 15. Among the dead was Col. Muthana al-Jabri, the chief of the Malaab police station, they said.

Later on, police said three suicide bombers drove their explosive-laden cars into the gate of the Anbar Operation Command, the military headquarters for the province, killing five soldiers and wounding 12.

Fierce clashes erupted between security forces and Islamic State militants following the attacks. Islamic State militants later seized Malaab after government forces withdrew, with the militants saying they now held the military headquarters.

A police officer who was in Malaab said retreating forces left behind about 30 army vehicles and weapons that included artillery and assault rifles. He said some two dozen police officers also went missing during the fighting.

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