Suicide bomb blasts tore through crowds waiting for food aid in central Baghdad and inside a roadside restaurant filled with Iranian pilgrims Thursday, killing at least 78 people in Iraq’s deadliest day in more than a year.

The toll — at least 31 dead in Baghdad and 47 to the north in Diyala province — follows a series of high-profile attacks this month blamed on Sunni insurgents. The violence highlights potential security gaps as Iraqi forces increasingly take the lead role from U.S. forces in protecting Baghdad and key areas around the capital.

The insurgent push is still nowhere near the scale of violence in past years, but it has undermined confidence that Iraq’s security gains were on solid footing at a time when the U.S. military is shifting its focus and resources to Afghanistan.

Iraqi authorities, meanwhile, say they have struck back at the heart of the insurgency: claiming they arrested one of the most wanted leaders of a militant network linked to al-Qaida.

The reported capture of Abu Omar al-Baghdadi, the head of the Islamic State of Iraq, could mark a setback to insurgents as they try to intensify attacks after a relative lull.

In the past, however, Iraqi officials have reported al-Baghdadi’s arrest or killing, only to acknowledge later that they were wrong. The U.S. military has even said al-Baghdadi could be a fictitious character used to give an Iraqi face to an organization dominated by foreign al-Qaida fighters.