A suicide bomber detonated an explosive vest at a dinner feast in western Baghdad's Abu Ghraib district, killing at least 21 people, police said.
Police colonel Dawood Suleiman in the nearby city of Fallujah gave the initial death toll as 21.
A police source in Baghdad who declined to give his name said 25 had died. Earlier the source had given a much lower figure.
Abu Ghraib is a largely Sunni Arab district located between central Baghdad and Fallujah on the main highway heading west from the capital, Reuters reported.