The attack hit Sunnis praying at a special service Sunday night during the holy Muslim month of Ramadan and appeared calculated to try to re-ignite widespread violence in Iraq just months before U.S. troops are to complete their withdrawal.
The bomber, who pretended to be a beggar, had attended prayers for six straight days at the Um al-Qura mosque in western Baghdad, said Sheik Ahmed Abdul Gafur al-Samarraie, head of an endowment that oversees all Sunni religious sites nationwide.
He said the bomber had a bandaged hand and appeared to pose no threat.
"When his face became familiar to the guards they didn't search him last night," al-Samarraie told reporters at the mosque, where blood still stained the marble floors and stairs.
He said guards first became suspicious when they saw the man moving through the crowd trying to get close to al-Samarraie and took him outside. But the man returned through a back door and blew himself up when he was a few steps away from al-Samarraie.