BAGHDAD (AP) — Iraqi police and army forces abandoned their posts in the northern city of Mosul after militants overran the provincial government headquarters and other key buildings, dealing a serious blow to Baghdad's efforts to control a widening insurgency in the country, a provincial official and residents said Tuesday.

The insurgents seized the government complex — a key symbol of state authority — late on Monday, following days of fighting in the country's second-largest city, a former al-Qaida stronghold situated in what has long been one of the more restive parts of Iraq. The gunmen also torched several of the city's police stations, freeing detainees held in lockups.

The fighters are believed to be affiliated with the Islamic State of Iraq and the Levant, an al-Qaida splinter group that is behind the bulk of the bloody attacks in Iraq and is among the most ruthless rebel forces fighting to topple President Bashar Assad in neighboring Syria. The group has also tried to position itself as a champion for Iraq's large and disaffected Sunni minority.

Several worried Mosul residents reported seeing the gunmen hoisting the black flags inscribed with the Islamic declaration used by ISIL, al-Qaida and other jihadist groups.

As the militants worked to consolidate control over Mosul, a powerful blast struck a funeral in the central city of Baqouba, about 60 kilometers (35 miles) northeast of Baghdad. The city, a onetime flashpoint between insurgents and U.S. forces, is home to both Sunnis and Shiites.

Police said the explosion targeted mourners gathered for the funeral of a Sunni university professor killed a day earlier, killing at least 15 and wounding 27. A hospital official confirmed the casualties.

All officials spoke on condition of anonymity because they weren't authorized to speak to the media.

In Mosul, 360 kilometers (225 miles) northwest of Baghdad, in Ninevah province, the insurgents appeared to be in control in several parts of the city, residents said over the telephone, speaking on condition of anonymity for fear of retribution.

Detainees set free form the police stations were seen running in the streets in their yellow-jumpsuits, they said.

Um Karam, a government employee who lives about two kilometers (just over a mile) from the provincial headquarters, said her family decided to flee the city early on Tuesday after hearing about the government building's fall.

"The situation is chaotic inside the city and there is nobody to help us," the Christian mother of two said, using a nickname out of concern for her safety. "We are afraid ... There is no police or army in Mosul."

The militants' push comes as Iraq's embattled Shiite prime minister, Nouri al-Maliki, struggles to hold onto power following parliamentary elections in late April that left him with the most seats but short of a majority needed to form a new government outright.

Many Iraqi Sunnis feel they have been marginalized under al-Maliki's leadership over the past eight years in power and see him as too closely aligned to Shiite conservatives and neighboring Shiite powerhouse Iran.

Ali Mahmoud, the media official for Ninevah province, said insurgents armed with machineguns and rocket-propelled grenade launchers stormed the provincial headquarters building in Mosul late on Monday night.

Mahmoud said they were able to overpower the building guards after a short firefight. He confirmed accounts by Mosul residents that many of the police and army forces that had been stationed in the city had disappeared by Tuesday.

Provincial governor Atheel al-Nujaifi was in a nearby guest house but managed to escape from the area unharmed, Mahmoud said. Atheel al-Nujaifi is the brother of Iraq's parliament speaker, Osama al-Nujaifi.

On Monday, the governor had urged residents to fend off the attackers.

"I call upon the men of Mosul to stand firm in their areas and to defend them against the strangers and to form public committees in their districts to help their people and to protect their areas," he said in a transcript of a speech posted online.

The governor himself has since left the city and is monitoring the situation, Mahmoud said.

Iraq has been grappling with its worst surge in violence since the sectarian bloodletting of 2006 and 2007.

ISIL insurgents and their allies remain in control of Fallujah and other parts of Anbar province, which neighbors Ninevah province and like it shares a long and loosely controlled border with Syria. The militants have also managed to launch frequent coordinated attacks in the capital, Baghdad, and in other parts of the country.

Insurgents last week launched an attack on the Sunni-dominated city of Samarra, 95 kilometers (60 miles) from Baghdad. They killed several members of the Iraqi security forces and took control of several districts before eventually being repelled.

A day later, militants occupied a university in Anbar province, taking dozens hostages before later releasing later on. Authorities in Anbar said Monday that about 15 staffers are still missing, likely held by a group of gunmen in a campus building.

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Schreck reported from Dubai, United Arab Emirates.