Gunmen in Iraqi army uniforms have killed the leader of one of Iraq's main Sunni Arab tribes, as well as three of his sons and his son-in-law. Officials said the pre-dawn attack on Wednesday in the Hurriyah area of northern Baghdad targeted the head of the influential Batta tribe. The Association of Muslim Scholars called the killings "cowardly." The Sunni organization also condemned a similar killing Tuesday in which a Sunni cleric and his brother were killed in a town , Khan Bani Saad northeast of Baghdad. In another development, a U.S. official said security concerns have been resolved and lawyers defending Saddam Hussein and seven co-defendants against massacre charges would be present Monday when the tribunal reconvenes. The defense lawyers had threatened to boycott the proceedings after two of their colleagues were killed.