Officials said Iraqi and U.S. units were closing in on leading Al Qaida operatives based in Baghdad. Last week, the spiritual leader of the Al Qaida network, identified as Ali Hussein Al Hayali, was captured northeast of Baghdad.

Al Qaida has been deemed the leading faction in the suicide car bombing campaign in Baghdad. Over the last week, at least 300 people, most of them Shi'ites, have been killed in the strikes.

Officials said a joint Iraqi-U.S. force detained Mohammed Hamad Kamal in downtown Baghdad last week. Kamal was said to have been the leading aide of Al Qaida network chief Abu Ayoub Al Masri.

On Sunday, the Iraqi military said Kamal was captured in the eastern sector of Baghdad. Brig. Gen. Kassem Atta, spokesman for the Baghdad security mission, said Kamal, known as "Abu Qatada the Palestinian," was arrested on Palestine St., regarded as a leading Sunni insurgency stronghold.

"The arrest was based on intelligence information," Atta said.

The U.S. military did not confirm the report. Over the last month, the Iraqi military reported the capture of several senior Al Qaida operatives, and later retracted the claims.

Officials said violence has been reduced around Iraq since the security mission began a month ago. Col. J.B. Burton, commander of the U.S. Army's 2nd Brigade Combat Team, 1st Infantry Division, has reported a significant decline in attacks in the provinces of Shula and Kadtimiya.

"Every day I go out and visit these joint security stations, I see better interoperability, increased command and control processes and increased sharing of information," Burton said. "What we started out with as a means to get coalition forces out into the battlefield has grown into a very promising effort to execute combined operations across western Baghdad."