Highlighting growing volatility north of Baghdad, suicide bombers have targeted US-backed neighbourhood patrols in two separate cities. One detonated at a checkpoint near a residential complex in Baiji, killing 23 people and wounding more than 70 others.
Local patrols, which are mainly Sunni and include many former insurgents, have been credited by the US military with helping to reduce violence in Iraq.
Yet they have increasingly come under attack by al Qaeda militants. A doctor in Baiji hospital said most of the casualties were civilians.
A suicide bomber also struck a funeral in the city of Baquba, killing 10 people and wounding five.
Police said the funeral was for a father and a son who had worked as armed volunteers with the US military.
They had been killed hours earlier in a shootout with US forces — by mistake, the Americans said.