Meanwhile four people died in a separate attack late Monday night inside Baghdad's fortified Green Zone, which houses the Iraqi government headquarters, as well as the US and British embassies.
The attack occurred as Americans were celebrating independence day at the US Embassy.
It follows a series of blasts and gun attacks during the past two days that have killed at least 10 police and soldiers.
(From GlobalPost in Iraq: The legacy of Iraq's bombed nuclear plant)
The Reuters news agency reported that two explosions at a municipal government building killed at least 27 people and wounded 50 others.
“It was a double explosion. The first was caused by a car bomb. We have no idea what the second was, whether a suicide bomber or a roadside bomb,” Taji municipality chief Raad al-Tamimi told Reuters.
“The place was crowded with people who were going to process official papers and with police and employees.”
Meanwhile a police officer told Al Jazeera that late Monday night, armed men fired a Katyusha rocket launcher into Baghdad's Green Zone, killing four and wounding 10 others.
The officer said the rocket hit a residential complex and sparked a fire.
The Green Zone is a regular target for mortar and Katyusha attacks by fighters.
In other violence Monday, armed rebels in a firing from a car killed a man near his house in the town of Rashad, near Kirkuk.
In another attack, two roadside bombs blew up outside a police officer's home in Haswa, south of Baghdad, killing one person. Also late Monday, gunmen shot dead a police officer near his house in the nearby town of Mussayab.
According to government figures, June recorded the highest monthly death toll of Iraqis so far in 2011, with 271 deaths.