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.