BAGHDAD — 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.
Thursday's attacks happened as American soldiers who specialize in clearing bombs from roads boarded a plane from Iraq to the Taliban heartland in southern Afghanistan, part of the largest movement of personnel and equipment between the two war fronts.
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.
A U.S. military could not confirm the arrest, said a spokesman, 1st Lt. John A. Brimley.
In 2007, Iraq's government reported that al-Baghdadi had been killed and released photos of what it said was his body. Later, security officials said they had arrested al-Baghdadi. In both cases, the U.S. military said at the time it could not be confirmed _ and the reports turned out not to be true.
The two attacks _ along with a suicide blast that killed three Sunnis who joined the anti-insurgent fight north of Baghdad _ made it the deadliest day in Iraq since March 8, 2008, when at least 110 people were killed.
The two main blasts Thursday carried separate messages.
The carnage in Baghdad showed insurgents were still capable of hitting the center of the capital. The devastated restaurant, to the north in Diyala province, was a reminder that the area remains an insurgent stronghold despite sustained offensives by U.S.-led forces.
Diyala _ with its good roads and proximity to Baghdad _ is considered a crucial gateway to the capital and a key to its security. U.S. commanders, facing a planned end of combat operations in August 2010, have dedicated increasing firepower to the region to try to cripple insurgent networks.
The Baghdad attacker hit about noon as police were distributing Iraqi Red Crescent food parcels in the central neighborhood of Karradah _ an area where many shops, restaurants and nightclubs have reopened in recent months as violence ebbed.
Police officials and staff members at Ibn al-Nafis hospital said at least 31 people were killed, including eight police officers, and that at least 50 were wounded. The officials spoke on condition of anonymity because they were not authorized to release the death toll.
It not immediately clear who carried out the attack, but one witness said it appeared to be a woman. Women have been used in suicide bombings in Iraq, most recently during a Feb. 13 attack on Shiite pilgrims.
Muhanad Harbi, a shop owner near the blast site, said he saw a woman wearing a black robe move into the crowd. He said it appeared she detonated an explosives belt.
Shanoon Humoud, 70, sat weeping among burned food packages scattered on the ground. Her husband, her son and two grandchildren were killed in the blast.
Humoud said she was in her apartment praying when she heard the blast.
"I came down to look for my relatives who were getting the food," she said. "But I couldn't find them."
Abbas Ibrahim, a 24-year-old college student, rushed to the scene, dodging through pools of blood and wincing at the smell of scorched human flesh.
"We regret that violence has come back to Baghdad," he said.
A spokesman for the Iraqi Red Crescent, Mohammad al-Khuzaie, called the attack "a brutal assault on humanitarian activities."
"We were trying to help the widows, orphans and divorced women when the blast occurred," he said.
North of Baghdad, the target was a crowded restaurant near Muqdadiyah, about 60 miles northeast of Baghdad, and a popular rest stop for Iranian pilgrims traveling by road to and from Shiite shrines in southern Iraq.
At least 47 people were killed and 69 were wounded, said U.S. military spokesman Derrick Cheng. Iraqi officials gave the same death toll.
Iranian state television reported that the blast killed about 35 Iranian pilgrims and wounded 60 others. It did not elaborate and there was no immediate reaction from Iranian officials.
Iraq's Shiite-led government has close ties to Tehran and has dedicated significant security resources to protect processions during major Shiite pilgrimages.
In January, a suicide bomber mingling among Iranian pilgrims killed more than three dozen people outside a mosque in Baghdad.
Associated Press Writers Sinan Salaheddin, Saad Abdul-Kadir and Hamid Ahmed in Baghdad, Nasser Karimi in Tehran, Iran, Pauline Jelinek in Washington and the AP News Research Center contributed to this report.