Tuesday's attack in Diwaniyah targeted security personnel as they were checking in for duty[Reuters]

At least 21 people have been killed in a suicide bombing attack outside the home of a local governor in central Iraq.

Two suicide bombers drove into the security gate of the Diwaniyah governorate building, where the governor's house is located, on Tuesday in Diwaniyah province, officials said. It is not known if the governor was there at the time.

One suicide bomber blew himself up and at least one car bomb exploded outside the governor's house as guards changed shifts at the checkpoint, the Reuters news agency reported.

"The initial death toll is 21 killed at a guard's checkpoint," Fadhel Mawat, a spokesman for the provincial
council told Reuters.

Kareem Isghair, the head of the security committee of Diwaniyah Provincial Council, said the explosions targeted security personnel as they were checking in for morning duty.

Most of the victims were bodyguards, officials said.

"This was a double suicide car bomb, obviously a very coordinated pre-planned attack," Al Jazeera's Jane Arraf reported from the capital, Baghdad.

"These car bombs exploded just outside the gate. Just beyond there is the governor's house and beyond that the provincial government buildings, so we can consider that this might have been an attack on the governor himself," she added. 

More than 20 other people were injured in the attack. The Iraqi interior ministry said the death toll was expected to rise.

Diwaniyah - 130km south of Baghdad - is a poor, mainly Shia region and several of Iraq's armed groups are active in the area.