At least 19 people have been killed and at least 60 injured in a series of blasts in the Iraqi capital, Baghdad.
About 100 Iraqis a day are dying in the civil violence
Three bombs hit the city centre early in the morning, killing nine. Hours later, two bombs exploded in a market, killing 10 and injuring dozens.
The attacks come despite a new security drive in the city.
Also on Tuesday, the Iraqi army assumed primary responsibility for security in an area of northern Iraq that includes the cities of Tikrit and Kirkuk.
String of bombs
The violence in Baghdad began at about 0645 local time with an explosion which hit a minibus and a taxi in the centre of the city, killing at least nine people.
Two other blasts targeted police, wounding three.
Four hours later, two bombs claimed at least 10 lives and injured at least 50 in a busy market in the al-Shurja district.
Tuesday also saw an armed raid on a bank in the capital. Robbers killed three security guards and two bank officials and escaped with a large quantity of money.
At least 11 other people were killed or found dead in Baghdad or other parts of Iraq. A US soldier died of wounds sustained in fighting, the US military said.
In Tikrit, the US commander in Iraq, Gen George Casey, and US ambassador Zalmay Khalilzhad attended a ceremony to transfer responsibility for security from the US 101st Airborne Division to the Fourth Iraqi Army Division.
In a statement, the two men said five of the Iraqi Army's 10 division headquarters were now responsible for security in their area, which they called an "important milestone".
They said coalition forces would continue to provide support to the Iraqi army.
The handover came a day after at least 4,000 US troops were deployed on the streets of the capital in an attempt to reduce sectarian killings and kidnappings.
Correspondents say the deployment is being seen as an admission that a two-month-old security operation involving 50,000 mostly Iraqi troops around Baghdad has failed to curb the violence.
Meanwhile, Iraqi Prime Minister Nouri Maliki sharply criticised a joint US-Iraqi operation in Sadr City, an area of Baghdad that is a stronghold of the Mehdi Army, a Shia militia.
US military officials said the raid, early on Monday, was aimed at "individuals involved in punishment and torture cell activities". Three people were captured in the raid, the US military said.
Iraqi police said three people, including a woman and child, were killed in the operation during which US aircraft carried out an air strike on a built-up area.
Mr Maliki said he was "very angered and pained" by the operation, warning that it could undermine his efforts toward national reconciliation.
"Reconciliation cannot go hand in hand with operations that violate the rights of citizens this way," Mr Maliki said in a statement on government television.
He apologised to the Iraqi people for the operation and said such incidents would not happen again.
In other violence, two Iraqi journalists have been found shot dead in Baghdad.
Mohammed Abbas Mohammed, who worked for a Shia newspaper, was shot dead in western Baghdad on Monday.
On the same day, police found the body of freelance journalist Ismael Amin, who was kidnapped two weeks ago.