Iraqi security officials said they captured one of the most wanted leaders of the Al Qaeda-linked Sunni insurgency Thursday, an arrest that could deliver a significant blow to an intensified campaign of attacks. Two separate homicide bombings killed at least 78 people.

The officials identified the arrested man as Abu Omar al-Baghdadi who leads the Islamic State of Iraq, an umbrella group of Sunni militant factions that is believed dominated by Al Qaeda in Iraq. However in the past, Iraqi officials have reported al-Baghdadi's arrest or killing, only to later say 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 Qaeda fighters.

U.S. officials could not immediately confirm the arrest.

Al-Baghdadi has been a key target for U.S. and Iraqi forces for years. But little is known about his origins or real influence over insurgent groups. The insurgents have staged a series of high-profile attacks in recent weeks, apparently including the two homicide blasts Thursday in Baghdad and north of the capital in Diyala province.

Iraqi state television quoted military spokesman Maj. Gen. Qassim al-Moussawi as saying al-Baghdadi was arrested in Baghdad. Security officials also told The Associated Press that he was captured.

In March, a 17-minute audio message attributed to al-Baghdadi called Washington's announcement of a combat withdrawal timetable from Iraq "recognition of defeat." The statement was carried on militant Web sites.

In Baghdad, a homicide bomber blew himself up among a group of Iraqis collecting humanitarian aid in a mainly Shiite area in Baghdad, killing at least 31 people, the Iraqi military said.

The attack was the latest in a series of high-profile bombings that have raised concern of an uptick in violence as the U.S. military scales back its forces before a planned withdrawal by the end of 2011.

The bombing occurred just after noon as Iraqi police were distributing aid parcels near Tahariyat Square in the central neighborhood of Karradah, according to the office of the main Baghdad military spokesman.

Abbas Ibrahim, a 24-year-old college student, described pools of blood on the ground and the smell of burned flesh in the air.

"We regret that violence has come back to Baghdad," he said.

Issam Salim, 35, was wounded by shrapnel as he was waiting for a bus about 30 yards from the explosion.

"I turned around as I fell to the ground and saw a big fire break out with black smoke," he said from his hospital bed. "Women and children are crying from pain beside me in the hospital. Some of them suffered burns."

Some police were among the 31 people killed and 51 other people were wounded, according the military.

Military spokesman Derrick Cheng said 47 people were killed and about 69 were wounded when another homicide bomber detonated an explosives vest near Muqdadiyah, an insurgent hotbed about 60 miles northeast of Baghdad.

Iraqi police and hospital officials said another 65 were wounded. Most of the wounded were pilgrims, the officials said.

Meanwhile, the U.S. military said at least 20 were killed. Conflicting casualty tolls are common.