BAGHDAD (Reuters) - A suicide bomber in an explosive vest killed 25 people at a dinner banquet in western Baghdad’s Sunni Arab Abu Ghraib district on Sunday, police said.

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The attack, the biggest in weeks, took place at the home of a local sheikh who was holding the feast to celebrate the release of his son from U.S. detention, police said.

They said women and children were among the dead, as were some men believed to be members of U.S.-backed neighborhood patrols.

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 later said 25 had died and 32 were injured.

Iraqi police said U.S. helicopters had flown in to evacuate the wounded.

Abu Ghraib is a largely Sunni Arab district located between central Baghdad and Fallujah on the highway heading west from the capital into Anbar province, an area once in the grip of al Qaeda but now controlled by U.S.-backed tribal groups.

U.S. and Iraqi authorities say suicide bombings are the signature tactic of al Qaeda Sunni Arab militants, who frequently target other Sunnis since Sunni tribes turned against them over the past two years.

Iraq has become far less dangerous over the past year, but militants still retain the capability to conduct large-scaled bombings.

Four roadside bombs in other parts of Iraq -- a double bomb attack in central Baghdad and two separate strikes in Diyala province north of the capital -- killed 11 people on Sunday.

Diyala, where U.S. forces say al Qaeda has regrouped since being pushed out of other parts of the country, has been the scene of a major crackdown by U.S.-backed Iraqi forces and a bombing campaign by militants over the past few weeks.