At least 68 people were killed and 200 wounded when co-ordinated car bomb attacks detonated at four police stations in the southern city of Basra.
The mayor of Basra, Wael Abdul-Hafeez told reporters most of the dead were civilians, including many children. He said 99 people were wounded. Hafeez accused Osama bin Laden's al Qaeda network of being behind the morning rush-hour blasts.
Near-simultaneous explosions hit three police stations in Basra and one in the town of Zubair, 25 km south of the mainly Shia city at around 7:15 a.m
A fourth explosion near the city's police academy went off two hours after the initial blasts but there was no immediate information on casualties.
A British Ministry of Defence spokeswoman in Basra said "All four attacks seem to have been carried out by suicide bombers."
Ten elementary school students whose bus was passing by the Saudia station at the time of the blast were among the dead, Iraqi Police Colonel Kadhem al-Muhammedawi said.
Iraq's Coalition Provisional Authority, which in Basra is British-led, said it would pursue those behind "these despicable attacks" and urged Iraqis to "isolate those who use violence to try to disrupt the restoration of Iraqi sovereignty".
A wounded Iraqi, Amin Dinar, said he had heard a huge explosion as he stood at the door of his house.
"I looked around and saw my leg bleeding and my neighbour lying dead on the floor, torn apart," he said from his hospital bed. "I saw a minibus full of children on fire."
The mayor, speaking at Basra police headquarters, said police had recovered the remains of one bearded bomber.
"I accuse al Qaeda," the mayor said. "We have arrested a person disguised in a police uniform. We are questioning him."
US officials have blamed al Qaeda or its affiliates for some of the violence sweeping Iraq.
Interior Minister Samir Sumaidy said the Basra attacks were similar to devastating suicide attacks in the Shia holy city of Kerbala and the Kurdish capital Arbil earlier this year. But he told a news conference it was too early to assign blame.