Baghdad, Iraq ? A tribal chief who challenged Iraq’s most feared terrorist and sent fighters to help U.S. troops battle al-Qaida in western Iraq died in a hail of bullets Sunday – the latest victim of an apparent insurgent campaign against Sunni Arabs who work with Americans.

Sheik Osama al-Jadaan was ambushed by gunmen as he was being driven in Baghdad’s Mansour district, a predominantly Sunni Arab area. Al-Jadaan’s driver and one of his bodyguards also were killed, police Lt. Maitham Abdul Razzaq said.

Al-Jadaan was a leader of the Karabila tribe, which has thousands of members in Anbar province, an insurgent hotbed stretching from west of Baghdad to the Syrian border. He had announced an agreement with the U.S.-backed Iraqi government to help security forces track down al-Qaida members and foreign fighters.

U.S. troops also raised a scout force from al-Jadaan’s followers known as the “Desert Protectors” to help find insurgents living under the protection of a rival tribe in Qaim and a cluster of nearby towns in Anbar. U.S. officials described the area as a staging ground for smuggling weapons, ammunition and fighters into Iraq.

Al-Jadaan claimed in March that his people had captured hundreds of foreign fighters and handed them over to authorities. He also issued a warning to al-Qaida in Iraq’s leader, Abu Musab al-Zarqawi, who is blamed for many of the country’s worst terror bombings.

“Under my leadership and that of our brothers in other tribes, we are getting close to the shelter of this terrorist,” al-Jadaan said. “We will capture him soon.”

The drive, dubbed Operation Tribal Chivalry, was designed to secure Iraq’s borders with Syria, Jordan and Saudi Arabia to prevent foreign fighters from sneaking in.