In Mahmoudiya, US troops arrested Shaikh Adnan Fahd, the head of the area's al-Ghrir tribe, according to his brother, Eissa Fahd. There was no comment from US officials. Also on Saturday, al-Qaida in Iraq claimed responsibility for Friday's attack outside Prime Minister Ibrahim al-Jaafari's Islamic Dawa Party offices in Baghdad's Mansour district. The posting on an Islamic website could not be verified.