Baghdad ? A double truck bombing Monday in Mosul and blasts in Baghdad brought the Iraqi death toll to more than 100 in four days, the worst spasm of violence the country has suffered since U.S. forces left the cities.

The Mosul bombing, like another Friday on the fringes of the ethnically tense city, targeted ethnic minorities, indicating that insurgents are seeking out relatively undefended targets to maximize casualties as the strapped Iraqi army focuses its efforts on more central areas.

The attacks in Mosul, which the U.S. military has called the last stronghold of al-Qaida, killed 28 people Monday and 44 on Friday. It’s the first time since the U.S. turned urban security over to the Iraqis on June 30 that insurgents have managed to stage two massive attacks in short order.