* Blasts follow deadliest attack in more than a year

* Come ahead of U.S. withdrawal from towns and cities

(Corrects location of suicide bombing to Abu Ghraib)

BAGHDAD, June 22 (Reuters) - Bombs killed at least 15 people across Iraq on Monday, security officials said, two days after a suicide truck bomb in the north of the country killed 73 people in the deadliest attack for more than a year.

The blasts came as the U.S. military prepares to withdraw from Iraqi towns and cities by the end of June, and they raise questions about the Iraqi security forces' ability to stand alone in the face of a stubborn insurgency.

A roadside bomb killed three people and wounded 30 in a market in north Baghdad's Shaab district, and a parked car bomb killed five people in Karrada in central Baghdad, police said.

Another roadside bomb tore through a minibus carrying high school students in Sadr City in the east of the capital, killing three and wounding 12, police said.

Blood covered the floor of the bus and its windows were smashed. The students had been on their way to sit their final exams before the summer holidays.

"What did these students do to deserve this? They're not politicians, Americans or policemen to be attacked," said witness Mohammed Yezen.

Violence has broadly fallen in Iraq over the last year, but analysts have said attacks are likely to intensify ahead of a parliamentary election due in January.

Iraqi Prime Minister Nuri al-Maliki has built his reputation on cutting violence, and has lauded the partial withdrawal of U.S. troops. In Baghdad, authorities have started to remove the concrete blast walls which have blighted the city for years.

He urged Iraqis on Saturday not to lose heart if insurgents took advantage of the U.S. pull-back to step up attacks.

In west Baghdad, a suicide bomber detonated himself outside the Abu Ghraib municipal council building, killing one person and wounding five, police said.

The army said a roadside bomb also killed three soldiers near the northern town of Khanaqin, disputed by Arabs and Kurds.

U.S. troops are due to leave Iraq completely by 2012 as part of a security pact signed by Baghdad and Washington last year. (Writing by Mohammed Abbas)

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