Among those killed were a senior al-Qaida in Iraq leader Abu Karrar, who is believed to be responsible for bombing attacks in Baghdad, The American Forces Press Service reported.

Navy Rear Adm. Gregory J. Smith, the spokesman for the Multinational Force Iraq, said Karrar was involved with the Diyala suicide-bombing network that included female suicide bombers.

Smith said coalition forces are investigating the use of women as suicide bombers.

"Coalition soldiers and our Iraqi partners remain focused on protecting the people of Baghdad, and the investigation into these three criminals and their extremist networks is continuing," Smith said. "Our investigation into al-Qaida's use of women as suicide bombers and our efforts to mitigate this threat also continues."

As for violence in the war-torn capital, Smith said deaths from ethno-sectarian violence in Baghdad are down 95 percent during the past 11 months, the news service reported.

"While the progress has been significant, we all know Baghdad is not safe from al-Qaida and other extremists," he said. "There is still much work to be done to secure Baghdad from extremism."