Baghdad (CNN) -- At least 13 people were killed Monday when a suicide bomber drove his vehicle into a security checkpoint at a prison in the Taji district of Baghdad, police officials said.
Twenty-eight others were injured in the attack, including prison guards and civilians.
An investigation is ongoing into the bombing. No groups have yet claimed responsibility, but the attack bears the hallmarks of al Qaeda in Iraq.
Separately, Baghdad police officials said two civilians were killed and four others were wounded Monday afternoon when a roadside bomb exploded near the Baghdad International Fair Complex in western Baghdad.
Also Monday, a mortar round landed inside the heavily fortified Green Zone, killing at least two people, police said. The round landed on the outdoor car park that belongs to the Iraqi Parliament compound and hit a car. No details on the victims were immediately available.
The Green Zone is in central Baghdad and houses Iraq's government offices and a number of embassies including those of the United Kingdom and United States.