Mourners gathered on Friday for the funeral of the leader of the Sunni Arab revolt against al-Qaida militants, who was assassinated just 10 days after meeting the US president in Iraq's Anbar province.
More than 1,500 mourners marched along the highway near the home of Abdul-Sattar Abu Risha, who was killed along with two bodyguards and a driver on Thursday by a bomb hidden near his house, just west of Ramadi.
Scores of Iraqi police and US military vehicles lined the route to protect the procession as it followed the black sports utility vehicle carrying the sheik's flag-draped coffin.
Mourners vowed revenge as they chanted along the 10 kilometre (6 mile) route to Risha's family cemetery, many of them crying.
No group claimed responsibility for the assassination, but it was widely assumed to have been carried out by al-Qaida, which had already killed four of Abu Risha's brothers and six other relatives for working with the US military.
The young sheik organised 25 Sunni Arab clans under the umbrella of the Anbar Awakening Council, an alliance against al-Qaida in Iraq, to drive militants from sanctuaries where they had flourished after the US-led invasion in 2003.
US officials credit Abu Risha and allied sheiks with a dramatic improvement in security in such Anbar flashpoints as Fallujah and Ramadi after years of American failure to subdue the extremists.
US officials now talk of using the Anbar model to organise tribal fighters elsewhere in Iraq.
US President George W Bush hailed Abu Risha's courage during his short September 3 visit to al-Asad Air Base, and vowed in his nationally televised address on Thursday night to help others carry on his work.
Many high-ranking officials were on hand for the funeral, including Iraq's interior and defence ministers and National Security Adviser Mouwaffak al-Rubaie.