A makeshift bomb went off on Saturday morning in Baghdad's Shiite Sadr City neighborhood, killing 19 people and wounding 58 others, an Interior Ministry source said.
"A home-made explosive charge detonated at about 7:00 a.m. ( 0300 GMT) among a crowd of construction workers, who gathered to be hired for daily works, in Baghdad's Sadr City slum," the source told Xinhua on condition of anonymity.
Earlier, the source put the casualty figure at 19 killed and 36 wounded.
The powerful blast also damaged several shops and nearby buildings, he said.
Iraqi security forces rushed to the scene and cordoned off the area, paving the way for ambulances to evacuate the casualties, he added.
The explosion occurred hours before the parliament is scheduled to meet on 11:00 a.m. (0700 GMT) to approve a new cabinet of national unity led by Shiite Prime Minister-designate Nuri al- Maliki.