KABUL - Afghan President Hamid Karzai on Wednesday described the reported of killing a teenager by US military as a tragedy and criticized it.

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"It is a tragic story and reading it hurts our feeling. This crime committed by those soldiers who are addicted with heroin and hashish," President Karzai said in his address at the graduation ceremony of over 20,000 teachers.

Some US soldiers, according to German influential magazine - Der Spiegel had intentionally killed a 15-years old teen in Afghanistan's southern Kandahar province last year as an entertainment activity.

The murderers, who was reported to cut off parts of the body of the boy to keep as memory of their participation in Afghan war, has confessed to the crime.

Pentagon, according to media reports, said in a statement released on Monday it had apologized for the gruesome incident committed by the so-called US troops.  

President Karzai in his speech also expressed condolence to the suffering of his countrymen and asked the newly graduated teachers to work hard and serve better the sons and daughters of the land.

He also called on Taliban militants not to target educational centers and students.

There are 8.3 million children go to school in Afghanistan, according to Minister for Education.