Five bicycle bombs exploded in a crowded market in Mahmudiyah, 30 kilometres south-west of Baghdad, as families were shopping for food for the traditional evening meal held during the month of Ramadan.
At least 20 people were killed and 30 wounded in the attack.
Earlier, a suicide bomber boarded a bus returning from one of Baghdad's largest markets and detonated a device that killed four people and wounded another 15.
In the United States, President George W. Bush said military tactics in Iraq would keep changing to deal with insurgents but he said the US would not abandon the goal of building a strong democracy.
He was speaking after a meeting with his top military commanders to discuss possible changes to US military strategy in Iraq.
There has been a 22 per cent rise in attacks in Baghdad this month and it's set to become the worst month for US fatalities with 78 US soldiers killed so far.
In a candid interview on Al-Jazeera television, senior US diplomat Alberto Fernandez said the US had shown "arrogance" and "stupidity" in Iraq but warned that failure in the Arab national would be disastrous for the entire region.
British junior Foreign Office minister Kim Howells said in a BBC radio interview that Iraqi police and soldiers would be ready to take over security from coalition troops within a year.
He was speaking as British troops remain on standby to re-enter the southern city of Amara. Security was handed back to local forces in August but they have struggled to quell activity by Shi'ite militia.