A car bomb has reportedly killed seven people and wounded 45 when it ripped through a crowded market in Baghdad's Shia Sadr City district.
The car bomb, detonated by remote control, was aimed at shoppers in the Shia slum's Mureydi market. The densely populated area is often targeted by Sunni militants.
Police said the casualty toll could rise.
The prime minister ordered the US and Iraqi military to lift a blockade of the impoverished district on Tuesday that was imposed after a US soldier of Iraqi descent was kidnapped by a powerful militia controlling much of the slum.
The US military believes Ahmed al-Taie, who was abducted 10 days ago, is still alive and being held by his captors.
US military spokesman Major General William Caldwell also told a news conference there was a "tremendous amount of political activity" underway to secure the release of the US soldier of Iraqi descent, who was kidnapped by gunmen while visiting relatives after leaving the security of the Green Zone.
Mr al-Taie, a 41-year-old linguist, was visiting family "including his Iraqi wife" when he was kidnapped. His family told reporters he was taken by Shia militiamen.
"At this point we believe the ones who kidnapped Ahmed currently still have him," Maj Caldwell told reporters.
Asked if the US military had been in contact either directly or indirectly with the kidnappers, Maj Caldwell said: "There is ongoing dialogue that is being done at different levels at this time, but it would be inappropriate for me to state with whom or at what level."
The checkpoints had brought gridlock to several parts of the city and drawn the ire of Sadr City residents who complained of collective punishment.