At least 13 people were killed and more than 100 wounded on Friday when two roadside bombs exploded in quick succession in a crowded Baghdad market, Iraqi police and hospital sources said, in the latest attack targeting Shi'ite Muslims this month.
A wave of bombings in June against mainly Shi'ite pilgrims and shrines has killed more than 130 people and fuelled fears that Iraq could slip back into sectarian bloodletting of the kind that has receded since its peak in 2006-07.
Tensions have run high after U.S. troops left in December as Shi'ite, Sunni and Kurdish political factions vie for power.
The first explosion struck Husseiniya, a market in a mainly Shi'ite area on the outskirts of the Iraqi capital, where people were shopping for groceries and other goods, sources said.
The second blast followed soon afterwards as security forces and civilians gathered to tend to the casualties from the first.
"Fruit and vegetables have been scattered everywhere. Some children were wounded," said Mudhaffar Khalaf, a policeman at the scene. "We have started to evacuate the injured people."
In the northern city of Samarra, home to a key Shi'ite shrine, a suicide car bomber detonated his explosives near the entrance of the city, killing one person and wounding 10 others, including seven Iranian pilgrims and three members of the security forces, a source in Samarra operations command said.
The explosion was followed by three mortar rounds fired into the same area, the source said, as well as a roadside bomb which targeted a nearby hospital and wounded three civilians.
Iraq's main political factions have been locked in a crisis since December, with opponents to Prime Minister Nuri al-Maliki accusing the Shi'ite leader of trying to consolidate power at their expense.
The attacks come as Maliki tries to fend off attempts by Sunni, Kurd and some Shi'ite rivals to organize a vote of no-confidence against him.
"Today's attacks have targeted predominantly Shi'ite areas once again ... This would indicate that a radical Sunni group was responsible, potentially one affiliated with al Qaeda, and the use of a suicide bomber in at least one of the attacks would also back this up," said John Drake, a London-based senior risk consultant with security firm AKE.