At least 25 people have been killed in Baghdad's Abu Ghraib district after a suicide bomber blew himself up at a feast held by a sheikh to celebrate his son's release from a US detention centre.

About 30 people were also wounded in the attack on Sunday, which targeted members of the US-backed Awakening groups and police who were attending the dinner, an interior ministry official said. 

Ayyid Salim al-Zubai, a local sheikh in the mainly Sunni area, had invited dozens of guests to the banquet in honour of his son, who had been released earlier in the day from Camp Bucca in southern Iraq, residents and police said.

The son had quarrelled with al-Qaeda members while in detention and may have been the target of the attack, residents said.

Awakening groups targeted

Aziz Moklif Ghatha al-Zubai, one of the local chiefs of the Awakening group who organised the dinner in the district's Al-Zaidan village, was killed in the attack.

Police cordoned off the area as victims were taken to a hospital in Falluja, 20km west of the city, eyewitnesses said.

Awakening groups began in the western province of Anbar when Sunni tribal leaders turned on their former al-Qaeda allies in 2006.

Hundreds of such groups have sprung up across Iraq since then, supported and paid for by the US military.

Al-Qaeda has frequently warned that members of Awakening groups will be specially targeted because of their co-operation with the US.