The increase in attacks comes in advance of a US-backed security crackdown.
A string of bomb blasts over the past three days have left more than 150 people dead, including 70 outside the capital's Mustansiriyah University on Tuesday.
"Bush's strategy has failed totally in Iraq"
Dimos, Hania-Crete, Greece
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George Bush, the US president, has tried to shore up support within his Republican party for his strategy to send about 21,500 extra US troops to Iraq to stabilise Baghdad and Anbar province.
Meanwhile, Nuri al-Maliki, Iraq's prime minister, told London's Times newspaper that Iraq's need for US troops could fall in three to six months if the US equipped Iraqi security forces with sufficient weapons.
In comments published on Thursday, he said: "I wish that we could receive strong messages of support from the US so we don't give some boost to the terrorists and make them feel that they might have achieved success."
The UN said earlier this week that more than 34,000 Iraqi civilians were killed in violence last year.
The Iraqi government has previously called UN data exaggerated.