BAGHDAD — Insurgents briefly raised the black flag of Al Qaeda in Iraq over a mostly Sunni neighborhood of Baghdad on Thursday during a brazen assault that killed 16 people and laid bare Iraq’s fragility as the withdrawal of U.S. troops accelerates and the country’s political crisis deepens.

Ten of the dead were from the security forces, four were members of the U.S.-allied Sunni militia Awakening, and two were civilians, according to the Ministry of Interior. In addition, at least 14 people were injured, and police said the casualty toll could rise as sporadic clashes between security forces and gunmen continued into the night.

The deaths of the seven soldiers and three policemen in Baghdad brought to 17 the total number of Iraqi security forces killed in incidents nationwide Thursday, underscoring the vulnerability of the security forces as U.S. troops are in the process of drawing down to a total of 50,000 by the end of August. Two Iraqi soldiers died in car bombings in Fallouja, four were killed in a suicide bombing north of Tikrit, and a policeman was shot dead in Mosul.

But it was the ferocious midafternoon battle in the former insurgent stronghold of Adhamiya in northern Baghdad that was […]