The worst attack took place in the Khakrez district of Kandahar province in southern Afghanistan, where a roadside bomb killed all 16 people traveling in a minibus, including eight children, said provincial police chief Abdul Raziq.

A string of attacks across Afghanistan, including one by a suicide bomber pushing an ice cream cart, killed at least 21 people on Saturday, as the U.N. said in a new report that May was the deadliest month for Afghan civilians since 2007.

The worst attack took place in the Khakrez district of Kandahar province in southern Afghanistan, where a roadside bomb killed all 16 people traveling in a minibus, including eight children, said provincial police chief Abdul Raziq.

He said the bomb was planted by the Taliban and was intended for NATO or Afghan forces.

In the eastern province of Khost, a suicide bomber blew himself up outside the local police headquarters in the Shai Kali area, killing three policemen and a child, according to provincial police chief Sadar Mohammad Zazai.

Among the four people killed in the blast was a local police chief, Mohammad Zahir Khan, Zazai said. It was not immediately clear whether Khan was specifically targeted. Provincial health director Hedayatullah Hamidi said 25 also were wounded in the attack.

A second suicide bomber, this one pushing an ice cream cart, killed one child and wounded three more in the central Afghanistan province of Ghazni, according to provincial police chief Mohammad Hussain.

“The suicide attacker was a young boy with a thin beard and mustache wearing a scarf,” said an eyewitness who identified himself as Asadullah. “He was pushing an ice cream cart. I was just standing 20 meters from him and then he exploded.”

The violence came the same day the United Nations released an interim report on civilian deaths that shows that last month 368 people were killed in the conflict and 593 were wounded, making May the deadliest month for Afghan civilians since 2007.

The U.N. said insurgents are responsible for 82 percent of those civilian deaths, while 12 percent were attributed to the international alliance and Afghan forces. Homemade bombs, such as the roadside device that struck the minibus in Kandahar on Saturday, were the leading cause of death, according to the report.

NATO airstrikes, a frequent cause of tension between the Afghan government and the alliance, were responsible for three percent of civilian deaths in May.

The U.N., which is preparing a midyear civilian casualty report for 2011, said it decided to release interim numbers because of the high rate of civilian killings in May.

Meanwhile, a bomb killed two policemen and wounded nine others who were investigating an earlier explosion late Friday at a satellite television network office in Mehterlam city in the eastern province of Laghman, said Faizelullah Patan, a spokesman for the provincial governor.

The Taliban announced its spring offensive several weeks ago and has been stepping up its attacks around the country. The insurgency has focused on Afghan security forces in a bid to undermine training and recruitment efforts of the international coalition, which hopes to transition security to the nascent Afghan force in targeted areas.

Security along Afghanistan’s border with Pakistan has been fraught, however, with Taliban fighters filtering in from Pakistan to stage spectacular attacks in the eastern part of the country.

Also on Saturday, NATO said an alliance service member died as a result of a noncombat related injury Friday in eastern Afghanistan. NATO did not release any other details about the death.

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