A series of bombings rocked Baghdad and some surrounding areas Saturday, killing at least 15 people and wounding at least another 27.

Iraqi officials say the first set of blasts went off near the town of Abu Ghraib, to the west of Baghdad, in an area frequented by day laborers. Officials said at least seven people were killed, including passengers in a truck carrying construction workers.

A few hours later, three bombs ripped through a marketplace in Baghdad's Bab al-Sharqi district, killing another 8 people and wounding at least 19 others.

The latest violence underscores Iraq's security challenges after remaining U.S. troops leave the country by the end of this year.

On Thursday, three bombings in the southern Iraqi city of Basra killed 19 people and wounded at least 65 others.

There was no immediate claim of responsibility for the bombings, but officials said most of the victims were soldiers and policemen.

Violence across Iraq has declined significantly since peaking in 2006 and 2007, but attacks remain common. More than 250 people were reported killed last month.