Dozens killed by car and suicide bombs in Iraqi cities
More than 70 people have been killed and many others injured in a series of bomb attacks across Iraq.
Baghdad was worst hit, with several explosions at bus stations and markets in the mainly Shia Muslim districts.
Attacks also occurred in Samarra, north of the capital, and Basra and Hilla further south.
It is one of the worst days of violence in recent months as Iraq has seen a rise in attacks linked to growing political and sectarian tension.
The bloodshed has raised fears of a re-emergence of the levels of sectarian violence seen in 2006 and 2007.
Prime Minister Nouri al-Maliki vowed to make immediate changes to Iraq's security strategy and told Iraqis that militants "will not be able to return us to the sectarian conflict".
In a separate incident, 10 policemen kidnapped on Saturday in western Anbar province were found dead.
'Showered with wreckage'
Monday's violence left more than 200 people injured.
One of the bloodiest attacks in Baghdad happened in the northern Shia neighbourhood of Shaab, when a car bomb exploded near a crowded market place killing at least 12 people and wounding more than 20.
The bombs in Basra, a mainly Shia Muslim city, killed at least 14 people outside a restaurant and the main bus station.
One of the injured, Mohammed Ali, said he was standing near a food cart in a crowded area "when all of a sudden it turned dark, dust filled the area".
"I was showered with metal wreckage and wounded in my legs," he told Reuters news agency.
Three people were killed and 15 wounded in a car bomb attack in Samarra, a city some 113km (70 miles) north of Baghdad. The blast reportedly happened near a gathering of members of the pro-government Sunni militia, the Awakening Council.
In the town of Balad, not far from Samarra, eight pilgrims from Iran - a mostly Shia country - were killed after the bus they were travelling in was hit by a car bomb blast.
In Hilla, 11 people were killed in bomb attacks on two Shia mosques during evening prayers.
No group has said it carried out Monday's attacks, but tension between the Shia Muslim majority, which leads the government, and minority Sunnis has been growing since last year.
Sunni demonstrators have accused the government of Prime Minister Maliki of discriminating against them - something the government denies.
Iraqis have not witnessed violence on the scale of the last few weeks for nearly five years, says the BBC's Aleem Maqbool in Baghdad.
The Shia-Sunni fault line, with Syria currently at its epicentre, is certainly contributing, he notes.
But Iraqis do not see their own politicians doing enough to unite people on both sides of the sectarian divide, and they do not see the international community showing the urgency they think it should in averting further chaos, our correspondent adds.
Violence has increased since more than 50 people died in clashes between security forces and Sunni Arabs in April, when an anti-government protest camp was raided in Nawija near Kirkuk.
At least 60 people died in three bombings in Sunni Muslim areas in and around Baghdad on Friday. Those bombings followed deadly attacks on Shia targets across Iraq.
On Sunday, at least 10 policemen were reported killed in north-western Iraq in attacks blamed by the authorities on Sunni militants.
Basra had been seen as relatively peaceful, but there too, violence has risen in recent months.
In March, a car bomb in the city killed 10 and wounded many others. On Saturday gunmen there shot and killed a Sunni Muslim cleric.