Story highlights Mohammed Khamis Abu Risha was head of the Ramadi Awakening Council

He was on patrol with Iraqi security forces in Ramadi when he was killed

He is the nephew of Sheikh Ahmed Abu Risha, head of the Anbar Awakening Council

The head of the Ramadi Awakening Council was killed Tuesday in a suicide bombing in Iraq's Anbar province, police officials told CNN.

Mohammed Khamis Abu Risha was on a joint patrol with Awakening Council members and Iraqi security forces when he was killed by a suicide bomber, the officials said. At least four others were also killed in the blast, they said.

Abu Risha has been among those leading the fight in Ramadi against the Islamic State of Iraq and Syria , a rogue al Qaeda group know by the acronym ISIS.

There was no immediate claim of responsibility. But ISIS has claimed to have carried out several failed assassination attempts against him in recent months.

Abu Risha is the nephew of Sheikh Ahmed Abu Risha , head of the Anbar Awakening Council -- a group composed primarily of Sunni Arab fighters who turned on al Qaeda in Iraq in late 2006 and joined forces with the U.S.-led coalition.

The sheikh took over as head of the province's Awakening Council after his brother Sheikh Abdul Sattar was assassinated in 2007.

While a number of the members of the council, also known as the Sons of Iraq, have been integrated into Iraq's security forces, the sheikh has said he maintains a militia of about 80,000. Iraq's government has put the number at 50,000, according to published reports.