A suicide bomber blew himself up and a car bomb exploded almost simultaneously outside the Diwaniya governor's house, 150 km (95 miles) south of Baghdad, just as guards changed shifts. Most of the victims were security staff, officials said.

Television footage showed the crumpled and burned-out wreckage of a white truck lying by the remains of a guard post. Bloodied and wounded security guards filled the beds of a local Diwaniya hospital.

Muayad al-Ansary, a spokesman for the provincial council in Diwaniya, said the death toll had risen to 25 killed and 35 more were wounded.

Bombings and killings in Iraq have fallen sharply since the height of sectarian violence in 2006-2007, but a stubborn Sunni Islamist insurgency linked to al Qaeda, other Sunni groups and rival Shi'ite militias still carry out daily attacks.